glapi: disable python escape sequences in strings that use invalid ones

We use invalid escape sequences in a few string.
r'...' disables escape sequences. This fixes validator errors:

/home/marek/dev/mesa/src/mapi/mapi_abi.py:45: SyntaxWarning: invalid escape sequence '\w'
  '^(?P<type>[\w\s*]+?)(?P<name>\w+)(\[(?P<array>\d+)\])?$')
/home/marek/dev/mesa/src/mapi/glapi/gen/api_exec_init.py:43: SyntaxWarning: invalid escape sequence '\p'
  header = """/**
/home/marek/dev/mesa/src/mapi/glapi/gen/gl_enums.py:64: SyntaxWarning: invalid escape sequence '\c'
  print("""

Reviewed-by: Adam Jackson <ajax@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/33634>
3 files changed