Remove commit sha from release inputs

[emmyoop]

Remove the commit sha from release inputs. We should always release the HEAD of the branch we release from.

We can never release anything except HEAD. If we tried, we end up merging in version and changelog updated into HEAD and then using the new HEAD with the updates included.

Example

- commit 003 HEAD
- commit 002
- commit 001

If we entered to release commit 001, the version bump and changelog generation would take place, we would merge those changes back in to the branch and now have (assuming no conflicts)

- commit 004 HEAD
- commit 003 
- commit 002
- commit 001

And would release commit 004 which would _include 002 which is not desirable. Removing commit sha as an input removes any confusion that this may be possible.

This will involve removing input from pre-release, changing logic to use HEAD in the build step, and updating core and all adapters to no longer take the commit sha as an input.