Align all .htaccess files to support Apache 2.4 mod_authz_core directives

While the main .htaccess as well as the ones in phpbb/db/migration/data/vXYZ/
do already support the Apache 2.4 mod_authz_core directive "Require all denied",
all others still use only the deprecated "Deny from All". To not force modern
system to use the mod_access_compat module, the modern directives should be
supported in every case.

For this, the method of phpbb/db/migration/data/vXYZ/.htaccess is copied to
update and align all .htaccess files across the source code.

Related pull request: https://github.com/phpbb/phpbb/pull/6023