CMake: Fix semicolon warnings for generated resource init code

Fixes clang warnings when -Wextra-semi-stmt is enabled.

Sample warning:

 warning: empty expression statement has no effect; remove
   unnecessary ';' to silence this warning [-Wextra-semi-stmt]
   resourceReferenceKeeper() { QT_KEEP_RESOURCE(qmake_foo); }

Amends 11259972a3

Pick-to: 6.7
Fixes: QTBUG-123588
Change-Id: I7ffc23cf00d8e2741e91c4d0b4056b0c89057dc2
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by:  Alexey Edelev <alexey.edelev@qt.io>

src/corelib/Qt6CoreResourceInit.in.cpp

@@ -9,6 +9,6 @@ QT_DECLARE_EXTERN_RESOURCE(@RESOURCE_NAME@)
 
 namespace {
     struct resourceReferenceKeeper {
-        resourceReferenceKeeper() { QT_KEEP_RESOURCE(@RESOURCE_NAME@); }
+        resourceReferenceKeeper() { QT_KEEP_RESOURCE(@RESOURCE_NAME@) }
     } resourceReferenceKeeperInstance;
 }