Downgrade ansible-core to <2.19

[bertiethorpe]

Local testing on macOS shows ansible-core 2.19 causes OpenTofu version parsing to fail:

  ansible_facts:
    terraform_available_versions: |-
      [
          ("/usr/local/bin/tofu", "1.9.1"),
        ]

TASK [azimuth_cloud.terraform.install : Filter Terraform versions] ****************************************************************************************************************************
Monday 01 September 2025  13:09:31 +0100 (0:00:00.046)       0:00:05.561 ****** 
[ERROR]: Task failed: Finalization of task args for 'ansible.builtin.set_fact' failed: Error while resolving value for 'terraform_acceptable_versions': object of type 'str' has no attribute 1

Downgrade to 2.18 fixed the issue

[AlexCK-STFC]

Closes #247 (partially, the templating issues need solving at some point)

The OpenTofu issue duplicates azimuth-cloud/ansible-collection-terraform#25

OpenTofu issue is solved by my PR azimuth-cloud/ansible-collection-terraform#26 but there's a bunch more templating issues with 2.19 so it should remain pinned until they are resolved.

[JohnGarbutt]

@bertiethorpe can you test out that change in here for us please?
azimuth-cloud/ansible-collection-terraform#26

[AlexCK-STFC]

@bertiethorpe can you test out that change in here for us please? azimuth-cloud/ansible-collection-terraform#26

This isn't the only templating broken by 2.19.

After making that fix, I tried deploying again and got yet another issue caused by 2.19 in the Slack webhook step:
#247

I'm betting additional fixes are needed after that too, I didn't have the capacity to do so so I just pinned for now. I think a lot of testing of each component is needed to ensure all roles and all tasks run properly on 2.19.

[JohnGarbutt]

Lets just get this in for now, to stop other issues