gppa-acf-repeater-mapper.php: Fixed an issue with regular expression.

[saifsultanc]

Context

⛑️ Ticket(s): https://secure.helpscout.net/conversation/2470092230/59496?folderId=3808239

Summary

A limitation with the ACF Repeater Mapper snippet if the repeater field has a number attached to the name.

So, if we processed for $key as meta_test_repeater_1_0_name. This will give us:

$repeater as test_repeater
$index as 1
$subfield as 0_name

This is because of the additional 1 attached to the name. The $repeater is actually test_repeater_1, $index is 0, and $subfield is name.

[claygriffiths]

This regex LGTM!