Documentation: kunit: fix example run_kunit func to allow spaces in args

Without the quoting, the example will mess up invocations like
$ run_kunit "Something with spaces"

Note: this example isn't valid, but if ever a usecase arises where a
flag argument might have spaces in it, it'll break.

Signed-off-by: Daniel Latypov <[e-mail]>
Reviewed-by: David Gow <[e-mail]>
Reviewed-by: Brendan Higgins <[e-mail]>
Signed-off-by: Shuah Khan <[e-mail]>

Documentation/dev-tools/kunit/running_tips.rst

···
 .. code-block:: bash
 
 	function run_kunit() {
-	  ( cd "$(git rev-parse --show-toplevel)" && ./tools/testing/kunit/kunit.py run $@ )
+	  ( cd "$(git rev-parse --show-toplevel)" && ./tools/testing/kunit/kunit.py run "$@" )
 	}
 
 .. note::