SubmittingPatches: Improve SubmittingPatches example

The example commit didn't show the convention of prefixing the message with
the relative directory path where the file lives, which has led new
contributors to innocently submit changes that aren't formatted ideally.
This adds a path to the example.

Signed-off-by: Anthony D'Atri <anthony.datri@gmail.com>

Author: anthonyeleven

SubmittingPatches.rst

@@ -173,7 +173,7 @@ able to refer to the bug tracker easily.
 
 Here is an example showing a properly-formed commit message::
 
-     doc: add "--foo" option to bar
+     doc/rados/mumble: Add "--foo" option to bar
 
      This commit updates the man page for bar with the newly added "--foo"
      option.