CppCheck: Tr::tr and code cosmetics

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

src/plugins/cppcheck/cppcheckrunner.cpp

@@ -11,8 +11,7 @@
 
 using namespace Utils;
 
-namespace Cppcheck {
-namespace Internal {
+namespace Cppcheck::Internal {
 
 CppcheckRunner::CppcheckRunner(CppcheckTool &tool) : m_tool(tool)
 {
@@ -149,5 +148,4 @@ void CppcheckRunner::handleDone()
         checkQueued();
 }
 
-} // namespace Internal
-} // namespace Cppcheck
+} // Cppcheck::Internal