[android] Fix compile with -warnings-are-errors

Remove unused variable

Change-Id: I64da66da0c17131de6280660576f2789696e86b3
Reviewed-by: Christian Stromme <christian.stromme@qt.io>

src/plugins/platforms/android/androidjniclipboard.cpp

@@ -47,7 +47,6 @@ namespace QtAndroidClipboard
 {
     QAndroidPlatformClipboard *m_manager = nullptr;
 
-    static char const *const QtNativeClassName = "org/qtproject/qt5/android/QtNative";
     static JNINativeMethod methods[] = {
         {"onClipboardDataChanged", "()V", (void *)onClipboardDataChanged}
     };