Commit 720ac2ef479d ("PATCH scripts/kernel-doc") fixed the two
instances of literal braces that Perl 5.28 warns about, but there are
still more than it doesn't warn about.
Escape all left braces that are treated as literal characters. Also
escape literal right braces, for consistency and to avoid
Braces are usually metacharacters in regexes, used to specify a
number of repetitions or as part of an escape sequence. If this
interpretation is not possible then Perl currently treats them
as literal characters.
Perl 5.28 has deprecated the literal interpretation of left braces,
and Perl 5.32 w
