Settings UI: Fix spelling error and make spell checker happy (#41403)

## Summary of the Pull Request

- Renames `NavigatablePage` to `NavigablePage` to fix a spelling error.
- Reverts related entries in `exclude.txt` that triggered a forbidden
pattern error in the spell checker.
- The spell checker does not allow PascalCase words like
`NavigatablePage` in `exclude.txt` because of its automatic casing
rules.

 
Regression: #41285

---------

Co-authored-by: vanzue <vanzue@outlook.com>

src/settings-ui/Settings.UI/Helpers/NavigablePage.cs

@@ -14,14 +14,14 @@ using Windows.UI;
 
 namespace Microsoft.PowerToys.Settings.UI.Helpers;
 
-public abstract partial class NavigatablePage : Page
+public abstract partial class NavigablePage : Page
 {
     private const int ExpandWaitDuration = 500;
     private const int AnimationDuration = 2000;
 
     private NavigationParams _pendingNavigationParams;
 
-    public NavigatablePage()
+    public NavigablePage()
     {
         Loaded += OnPageLoaded;
     }