watchflakes: incomplete example and minor text cleanup Affected page: https://go.dev/wiki/Watchflakes Change-Id: I53346de0dbdfeb67fb182016325f8f05038efc74 GitHub-Last-Rev: 4e63cd0e403143291a1c31f0804c02af8daa14cc GitHub-Pull-Request: golang/wiki#78 Reviewed-on: https://go-review.googlesource.com/c/wiki/+/735020 Reviewed-by: Sean Liao <sean@liao.dev>