tests: fix previously accidentally matching regexes in test-touch.t Before Mercurial commit 6d5718e39657 (run-tests: make "| foo (re)" not match everything, 2017-11-29), regexes like "| foo", which are common in graphlog output, would incorrectly match anything. After that commit, they match as they should, meaning that either "" or " foo" would match, but not a "| foo". This commit fixes the test by replacing the "|" by "." rather than escaping with "\|" since that would make the graph harder to read.