fix a few regexps that are better as raw strings

[dhalbert]

@elpekenin noticed this problem:

$ make fetch-all-submodules 
python3 tools/ci_fetch_deps.py all
/home/elpekenin/circuitpython/tools/ci_fetch_deps.py:14: SyntaxWarning: invalid escape sequence '\.'
  version_str = re.search("([0-9]\.*)*[0-9]", version_str).group(0)

That regexp should be a raw string. The vast majority of regexp strings are now raw strings, but I found a few more. A new were not really necessary, but made them raw strings for consistency, and one is easier to understand as a raw string.

[tannewt]

Thank you!