Merge branch 'develop-olympus' into develop

* develop-olympus:
  [ticket/11814] Remove redundant text from the topic reply email notification.
Replace utf_normalizer by intl's one, with patchwork/utf8 as fallback
Remove utf8_str_replace
Rely on mbstring, using patchwork/utf8 as fallback
Explicit UTF-8 charset on mbstring uses