qdoc: Fix MSVC warnings about '*/' found outside of comment

Add space, fixing:
qttools\src\qdoc\codemarker.h(52): warning C4138: '*/' found outside of comment
qttools\src\qdoc\codemarker.h(54): warning C4138: '*/' found outside of comment
qttools\src\qdoc\codemarker.h(55): warning C4138: '*/' found outside of comment
...

Change-Id: I1b53fadc09f47146738fe9e8c444ba874f048a97
Reviewed-by: Paul Wicking <paul.wicking@qt.io>