GOVERNANCE: Fix "motion to release" link target (to RELEASES.md)

[wking]

trafficstars

I'd garbled the old '#release-approval' target in c732cc2e (#15).

I expect this is a small enough change that it doesn't need the full amendment procedure, but it can certainly go out to an all-OCI-maintainer vote if folks would rather do it that way ;).

[wking]

This, like #34, falls into the "trivial broken link" category.