fix: update obsolete transaction isolation level attribute for aurora…

[Julien4218]

…/mysql

What was changed

The tx_transaction is no longer available with the most recent aurora/mysql version.
That attribute is now replaced with transaction_isolation.
AWS documentation for reference https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/AuroraMySQL.Reference.ParameterGroups.html
I've tested this change on the most recent aurora/mysql version 8.0.mysql_aurora.3.06.0

Why?

Without this change the temporal servers won't start. Here is the error message from one of the pod crashing:

Error 1193: Unknown system variable 'tx_isolation'

Checklist

1. Closes

2. How was this tested:

On latest Aurora/MySQL version version 8.0.mysql_aurora.3.06.0 with temporal version 1.30.0

3. Any docs updates needed?

[CLAassistant]

All committers have signed the CLA.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[robholland]

Please sign the CLA.