Docs workflow currently tries to deploy on pull requests

[matt-graham]

Describe the Bug

Currently the documentation workflow defined in .github/workflows/docs.yaml is set to try deploy built documentation in all workflow runs irrespective of triggering event. This causes workflow to fail on pull-requests as the associated deployment environment is configured to only allow deployment from default (main) branch.

To Reproduce

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Expected Behaviour

Docs workflow deploy job not run on PRs

Actual Behaviour

Docs workflow deploy job tries to run and fails on PRs

Version In Use

Additional Context

- Python version:
- Operating system: