Fix typo in quicknanobrowser.pro

Remove ContextMenuExtras.qml entry from the project file
of the quicknanobrowser. It is unnecessary after the quicknanobrowser
fork.

Change-Id: I87055413392e14817429678f29b520e55cafbbd1
Reviewed-by: Andras Becsi <andras.becsi@digia.com>

examples/webengine/quicknanobrowser/quicknanobrowser.pro

@@ -6,8 +6,7 @@ HEADERS = quickwindow.h \
 SOURCES = quickwindow.cpp \
           main.cpp
 
-OTHER_FILES += ContextMenuExtras.qml \
-               quickwindow.qml
+OTHER_FILES += quickwindow.qml
 
 RESOURCES += resources.qrc