python: fix regex strings

[MaxGyver83]

Use raw strings to get rid of these warnings:

$ python vim-plugins-profile.py
/tmp/vim-plugins-profile.py:105: SyntaxWarning: invalid escape sequence '\d'
  matches = re.findall("^\d+.\d+\s+\d+.\d+\s+\d+.\d+: "
/tmp/vim-plugins-profile.py:132: SyntaxWarning: invalid escape sequence '\d'
  matches = re.findall("^\d+.\d+\s+\d+.\d+\s+(\d+.\d+): "
/tmp/vim-plugins-profile.py:151: SyntaxWarning: invalid escape sequence '\d'
  matches = re.findall("^\d+.\d+\s+\d+.\d+\s+(\d+.\d+): "
Running vim to generate startup logs... done.
...

The solution is to use Python’s raw string notation for regular expression patterns; backslashes are not handled in any special way in a string literal prefixed with 'r'. So r"\n" is a two-character string containing '\' and 'n', while "\n" is a one-character string containing a newline. Usually patterns will be expressed in Python code using this raw string notation.

re — Regular expression operations — Python 3.13.0 documentation