[NO-ISSUE] ci: run governance once per commit (drop push trigger on dev)

[robsongajunior]

Summary

Every commit landing on dev currently runs the Governance Pipeline twice: once via push on dev and once via pull_request synchronize on the standing dev → main release PR (see the duplicated checks on #768). This drops dev from the push trigger so each commit is validated once.

• pull_request: [main, dev] stays — it feeds the required status checks for feature PRs and for the release PR, and validates the merge ref.
• push: [main] stays — post-merge sanity run on main (fires with the release PR already closed, so it never duplicates).

Notes

• No jobs in governance.yml branch on github.event_name / github.ref, so nothing depended on the push-on-dev run.
• ci type → no version bump.
• Caveat: a direct push to dev (outside a PR, with no open release PR) would skip governance; the repo flow is PR-only, and "require branch up to date" on dev covers the stale-merge gap.