clang-tidy modernize-concat-nested-namespace in cppcanvas..cppuhelper

Change-Id: I0bb4ea91288a15fb590d077fb390c53be8b50400
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/86801
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

cppcanvas/source/mtfrenderer/implrenderer.cxx

@@ -228,9 +228,7 @@ namespace
     }
 }
 
-namespace cppcanvas
-{
-    namespace internal
+namespace cppcanvas::internal
     {
         // state stack manipulators
 
@@ -3072,6 +3070,5 @@ namespace cppcanvas
             }
         }
     }
-}
 
 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */