Remove duplicate WebScopedUserGesture.cpp entry from web.gyp

Source/web/web.gypi

 {
   'variables': {
     'web_files': [
       'AssertMatchingEnums.cpp',
       'AssociatedURLLoader.cpp',
       'AssociatedURLLoader.h',
       'BackForwardClientImpl.cpp',
       'BackForwardClientImpl.h',
       'ChromeClientImpl.cpp',
       'ChromeClientImpl.h',
@@ skipping 196 matching lines @@
       'WebPluginScrollbarImpl.cpp',
       'WebPluginScrollbarImpl.h',
       'WebPopupMenuImpl.cpp',
       'WebPopupMenuImpl.h',
       'WebRange.cpp',
       'WebRemoteFrameImpl.cpp',
       'WebRemoteFrameImpl.h',
       'WebRuntimeFeatures.cpp',
       'WebScopedMicrotaskSuppression.cpp',
       'WebScopedUserGesture.cpp',
-      'WebScopedUserGesture.cpp',
       'WebScopedWindowFocusAllowedIndicator.cpp',
       'WebScriptBindings.cpp',
       'WebScriptController.cpp',
       'WebScrollbarThemePainter.cpp',
       'WebSearchableFormData.cpp',
       'WebSecurityOrigin.cpp',
       'WebSecurityPolicy.cpp',
       'WebSelectElement.cpp',
       'WebSelector.cpp',
       'WebSerializedScriptValue.cpp',
@@ skipping 112 matching lines @@
       ['os_posix==1 and OS!="mac"',
         {
           'web_unittest_files': [
             'tests/LocaleICUTest.cpp',
           ],
         }
       ],
     ],
   },
 }