The yum module within ansible requires the python yum bindings to work, and those are only available using Python 2.6. ansible-core 2.13 no longer supports Python 2.6, so there is no combination where you can use the yum module with ansible-core 2.13 on RHEL6.
The last version of ansible-core to support Python 2.6 for target execution was ansible-core 2.12.
Note that ansible-core 2.12 is the default available version on RHEL
8, because it's compatible with the built-in python 3.6, and is
available from Red Hat repos as an RPM. So it's a supportable release
on your ansible server, even if your server is on a commercially
supported RHEL.