update ansible pinned version

[marcoieni]

The previous version is not compatible with python 3.14.

I got the following error when applying #982:

TASK [Ensure bastion unprivileged users are configured] ************************************
fatal: [bastion.docs-rs-staging.rust-lang.net]: FAILED! => {"msg": "The conditional check 'vars_bastion_unprivileged_users | default([]) | length > 0' failed. The error was: Invalid conditional detected: module 'ast' has no attribute 'Str'"}

I updated to a couple of versions more and the error doesn't happen anymore.
To migrate, run rm -rf ansible/.venv and run the apply script again.