/opt/cpanel/ea-php56/root/etc/php.d/local.iniSimilarly, you can find the local.ini file for any other version under /opt/cpanel/ea-php** folder.
Comment the line:
extension=timezonedb.so
with
;extension=timezonedb.soOnce done, propagate the changes by remounting cagefs:
cagefsctl -M
If it still doesn't work, you would need to reinitialize the cagefs with the following:
cagefsctl -r
(https://docs.cloudlinux.com/index.html?cagefs_command_line_tools.html)
Once done, restart your apache, and should see the warning is gone.