CppCheck: Tr::tr and code cosmetics

Change-Id: I5e6583984f7dc94e998df3c20840f2ba2e801ab8
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>

src/plugins/cppcheck/cppcheckplugin.h

@@ -7,8 +7,7 @@
 
 #include <memory>
 
-namespace Cppcheck {
-namespace Internal {
+namespace Cppcheck::Internal {
 
 class CppcheckPluginPrivate;
 
@@ -27,5 +26,4 @@ private:
     std::unique_ptr<CppcheckPluginPrivate> d;
 };
 
-} // namespace Internal
-} // namespace Cppcheck
+} // Cppcheck