chore: Update SUPPORT_POLICY.rst to move 2.x to maintenance mode

[kessplas]

Issue #, if available:

Description of changes:

now that the DB-ESDK 3.x has been released, 2.x will be moved into maintenance mode in 6 months per the AWS SDKs and Tools Maintenance Policy.

Also move 1.x into End of Support, as the status date has passed.

EDIT: Moving this to draft until we have better documentation around version support.

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