doc: inverse major and minor

In the example, the major an minor keyword were set in a strange order. I changed it to stay consistent with PEP

Author: 12rambau

docs/bump.md

@@ -199,7 +199,7 @@ In your `pyproject.toml` or `.cz.toml`
 
 ```toml
 [tool.commitizen]
-tag_format = "v$minor.$major.$patch$prerelease"
+tag_format = "v$major.$minor.$patch$prerelease"
 ```
 
 The variables must be preceded by a `$` sign.