The "Check markdown format" work flow does not properly fail

[rmetzman]

The "Check markdown format" step in the github presubmits does not properly fail at that step if there is a diff in the expected format, it fails at the next step which is confusing to figure out what caused the problem.

Specifically this is the command in the ci.yaml file: "npx --yes prettier --write --prose-wrap always *.md"

If it needs to be run, it fails at the next step (Check that all markdown is up to date) which makes the error message ambiguous because it says "git status -s && test -z "$(git status -s)" instead of that the previous command needs to be run to fix the formatting.