oniguruma: bump to 6.9.9

oniguruma: bump to 6.9.9

Featured changes:
- Update Unicode version 15.1.0
- NEW API: ONIG_OPTION_MATCH_WHOLE_STRING
- Fixed: (?I) option was not enabled for character classes (Issue #264).
- Changed specification to check for incorrect POSIX bracket (Issue
  #253).
- Changed [[:punct:]] in Unicode encodings to be compatible with POSIX
  definition. (Issue #268)
- Fixed: ONIG_OPTION_FIND_LONGEST behavior
--- 6.9.8
- Whole options
  - (?C) : ONIG_OPTION_DONT_CAPTURE_GROUP
  - (?I) : ONIG_OPTION_IGNORECASE_IS_ASCII
  - (?L) : ONIG_OPTION_FIND_LONGEST
- Fixed some problems found by OSS-Fuzz

Signed-off-by: Eneas U de Queiroz <cotequeiroz@gmail.com>