Bug 1639613 - Pre: Fix potential typo: lastUsed -> lastused. r=mhowell

It's not 100% clear that this has any effect -- it might be that the
string is case insensitive -- but in any case let's keep our source
code uniform.

Differential Revision: https://phabricator.services.mozilla.com/D94774

browser/installer/windows/nsis/uninstaller.nsi

@@ -251,7 +251,7 @@ Function un.UninstallServiceIfNotUsed
   ; Restore back the registry view
   ${If} ${RunningX64}
   ${OrIf} ${IsNativeARM64}
-    SetRegView lastUsed
+    SetRegView lastused
   ${EndIf}
 
   ${If} $0 == 0