Remove nmusgrave@google.com from...

Remove nmusgrave@google.com from libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/OWNERS

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If this change is unnecessary or in error, vote the lowest CR value
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See the owner's recent activity for context:
https://android-review.googlesource.com/q/nmusgrave@google.com

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Change-Id: Idb86e5e0836ab51b59ae214059286a4c5897a970