message: docs: Fix unescaped `[` in character class
  Compiling the regex as it was documented before results in:
  > Syntax("Error parsing regex near \'-/:-@[-`{-\' at character offset 7: Use of unescaped \'[\' in character class is not allowed.")
diff: @@ -430,7 +430,7 @@ These classes are based on the definitions provided in
  [[:graph:]] graphical ([!-~])
  [[:lower:]] lower case ([a-z])
  [[:print:]] printable ([ -~])
  -[[:punct:]] punctuation ([!-/:-@[-`{-~])
  +[[:punct:]] punctuation ([!-/:-@\[-`{-~])
  [[:space:]] whitespace ([\t\n\v\f\r ])
  [[:upper:]] upper case ([A-Z])
  [[:word:]] word characters ([0-9A-Za-z_])
  