fix spell complain (#42379)

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## Summary of the Pull Request

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## PR Checklist

- [ ] Closes: #xxx
- [ ] **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

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## Detailed Description of the Pull Request / Additional comments

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## Validation Steps Performed

- Spell check should not complain

.github/actions/spell-check/expect.txt

@@ -369,9 +369,8 @@ devmgmt
 DEVMODE
 DEVMODEW
 devpal
-DFX
+dfx
 DIALOGEX
-diffs
 digicert
 DINORMAL
 DISABLEASACTIONKEY
@@ -508,6 +507,7 @@ eyetracker
 FANCYZONESDRAWLAYOUTTEST
 FANCYZONESEDITOR
 FARPROC
+fdx
 fesf
 FFFF
 FILEEXPLORER
@@ -1149,6 +1149,7 @@ ntfs
 NTSTATUS
 NTSYSAPI
 NULLCURSOR
+nullref
 nullonfailure
 numberbox
 nwc
@@ -1980,7 +1981,7 @@ WORKSPACESEDITOR
 WORKSPACESLAUNCHER
 WORKSPACESSNAPSHOTTOOL
 WORKSPACESWINDOWARRANGER
-Worktree
+worktree
 wox
 wparam
 wpf