mail/phpmailer[6|7]: fix pkg-plist for NLS option

All %%DATADIR%% entries were changed to %%NLS%%%%DATADIR%%.
Previously, disabling NLS caused missing language files listed in
pkg-plist and resulted in check-plist failures.
The port now works correctly with both enabled and disabled NLS.

PR: 248341
Sponsored by: Netzkommune GmbH