Cleanup unused branches

[dblock]

Coming from opensearch-project/opensearch-clients#64, cleanup unused branches.

For some unused branches we probably want to save state, so maybe note the last revision of any branch being deleted in this issue as it's being closed.

[nhtruong]

@dblock I do not have the permission to delete branches on this repo. We're no longer making releases for anything before 3.0, where we merged multiple gems into one and turned this into a single-gem repo, as our release pipeline no longer supports multi-gem release, and those branches are very stale. Would you mind deleting the following branches?

• 1.0
• 1.x
• 2.0
• bump-2.0.2

[dblock]

@nhtruong work with @opensearch-project/admin

[nhtruong]

@gaiksaya, would you mind delete the branches mentioned in this comment for this repo? Thank you.

[gaiksaya]

Above branches have been deleted. Thanks @nhtruong for the 2PR.