Quick accent character set fixes (#43504)

<!-- Enter a brief description/summary of your PR here. What does it
fix/what does it change/how was it tested (even manually, if necessary)?
-->
## Summary of the Pull Request
* Fix double uppercase theta character
* Fix some redundant special symbols

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## PR Checklist

- [x] Closes: #43457 #43137 #41570
- [ ] **Communication:** I've discussed this with core contributors
already. If the work hasn't been agreed, this work might be rejected
- [ ] **Tests:** Added/updated and all pass
- [ ] **Localization:** All end-user-facing strings can be localized
- [ ] **Dev docs:** Added/updated
- [ ] **New binaries:** Added on the required places
- [ ] [JSON for
signing](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ESRPSigning_core.json)
for new binaries
- [ ] [WXS for
installer](https://github.com/microsoft/PowerToys/blob/main/installer/PowerToysSetup/Product.wxs)
for new binaries and localization folder
- [ ] [YML for CI
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ci/templates/build-powertoys-steps.yml)
for new test projects
- [ ] [YML for signed
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/release.yml)
- [ ] **Documentation updated:** If checked, please file a pull request
on [our docs
repo](https://github.com/MicrosoftDocs/windows-uwp/tree/docs/hub/powertoys)
and link it here: #xxx

src/modules/poweraccent/PowerAccent.Core/Languages.cs

@@ -230,7 +230,7 @@ namespace PowerAccent.Core
                 LetterKey.VK_SLASH_ => new[] { "÷", "√" },
                 LetterKey.VK_DIVIDE_ => new[] { "÷", "√" },
                 LetterKey.VK_MULTIPLY_ => new[] { "×", "⋅" },
-                LetterKey.VK_PLUS => new[] { "≤", "≥", "≠", "≈", "≙", "⊕", "⊗", "∓", "≅", "≡" },
+                LetterKey.VK_PLUS => new[] { "≤", "≥", "≠", "≈", "≙", "⊕", "⊗", "±", "≅", "≡", "₊", "⁺" },
                 LetterKey.VK_BACKSLASH => new[] { "`", "~" },
                 _ => Array.Empty<string>(),
             };
@@ -546,10 +546,9 @@ namespace PowerAccent.Core
                 LetterKey.VK_E => new[] { "é", "ê", "€" },
                 LetterKey.VK_I => new[] { "í" },
                 LetterKey.VK_O => new[] { "ô", "ó", "õ", "º" },
-                LetterKey.VK_P => new[] { "π" },
                 LetterKey.VK_S => new[] { "$" },
                 LetterKey.VK_U => new[] { "ú" },
-                LetterKey.VK_COMMA => new[] { "≤", "≥", "≠", "≈", "≙", "±", "₊", "⁺", "“", "”", "‘", "’", "«", "»" },
+                LetterKey.VK_COMMA => new[] { "“", "”", "‘", "’", "«", "»" },
                 _ => Array.Empty<string>(),
             };
         }
@@ -728,7 +727,7 @@ namespace PowerAccent.Core
                 LetterKey.VK_Y => new[] { "ױ" },
                 LetterKey.VK_COMMA => new[] { "”", "’", "'", "״", "׳" },
                 LetterKey.VK_PERIOD => new[] { "\u05ab", "\u05bd", "\u05bf" },
-                LetterKey.VK_MINUS => new[] { "–", "־" },
+                LetterKey.VK_MINUS => new[] { "־" },
                 _ => Array.Empty<string>(),
             };
         }

src/modules/poweraccent/PowerAccent.Core/PowerAccent.cs

@@ -358,20 +358,21 @@ public partial class PowerAccent : IDisposable
 
     public static string[] ToUpper(string[] array)
     {
-        string[] result = new string[array.Length];
+        List<string> result = new(array.Length);
         for (int i = 0; i < array.Length; i++)
         {
             switch (array[i])
             {
-                case "ß": result[i] = "ẞ"; break;
-                case "ǰ": result[i] = "J\u030c"; break;
-                case "ı\u0307\u0304": result[i] = "İ\u0304"; break;
-                case "ı": result[i] = "İ"; break;
-                case "ᵛ": result[i] = "ⱽ"; break;
-                default: result[i] = array[i].ToUpper(System.Globalization.CultureInfo.InvariantCulture); break;
+                case "ß": result.Add("ẞ"); break;
+                case "ǰ": result.Add("J\u030c"); break;
+                case "ı\u0307\u0304": result.Add("İ\u0304"); break;
+                case "ı": result.Add("İ"); break;
+                case "ᵛ": result.Add("ⱽ"); break;
+                case "ϑ": break;
+                default: result.Add(array[i].ToUpper(CultureInfo.InvariantCulture)); break;
             }
         }
 
-        return result;
+        return [..result];
     }
 }