Update CONTRIBUTING.md

CONTRIBUTING.md

@@ -59,5 +59,5 @@ Then proceed with one of the following steps:
 2. increase the version number X.Y.Z in the file config.cmake 
 3. commit the changed config.cmake file
 4. add a tag with 'git tag -a "vX.Y.Z" -m"vX.Y.Z"'
-5. push with 'git push && git push --tags'
+5. push with `git push && git push --tags`
 6. The H2T jenkins server will automatically build a new simox package
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