[PLAT-193] Fix python sdk publish to pypi gha

[winnie-opal]

The publish to pypi workflow was silently broken and attempts to publish every release as 1.0.0 which gets skipped since it already exists.

The OpenAPI generator upgrade from 7.10.0 to 7.19.0 changed the pyproject.toml format from [tool.poetry] to the standard [project] table which causes the hardcoded version = "1.0.0" to override the old versioning logic.

See workflow run here https://github.com/opalsecurity/opal-python/actions/runs/24752948149/job/72419853149

This replaces that hardcoded version = "1.0.0" to ["version"]. This also updates the workflow to specify fetch-tags: true in the checkout so the workflow can use the git tag for the version.

Tested this locally to confirm that new builds use the existing tag

[winnie-opal]

• [PLAT-193] Fix python sdk publish to pypi gha #43 👈 (View in Graphite)
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