fix(php): Set error_log to empty value as is PHP's default, instead of invalid directory

Problem: the PHP error_log wants to log into /var/log/php/cli-error.log, which is not correct for FPM and also the folder /var/log/php does not exist.

We want to use the default behavior of PHP by leaving error_log empty.

• On FPM the error log will go into the Nginx error_log file per site, which is ok.
• On CLI the error will pre printed to stderr for the command output, which is also better.

Updating the ini files to avoid confusion, because right now the path is invalid. I assume PHP falls back to default behavior printing to stderr.