[Backport 2.11] Add release notes for v2.11.1

[opensearch-trigger-bot[bot]]

Backport ba69ebf9c06393ee640bf685b19e54d58dfb95d6 from #602

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (eeec44a) 68.48% compared to head (d365898) 68.56%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## 2.11 #604 +/- ## ============================================ + Coverage 68.48% 68.56% +0.08% Complexity 365 365 ============================================ Files 44 44 Lines 2481 2481 Branches 172 172 ============================================ + Hits 1699 1701 +2 + Misses 678 677 -1 + Partials 104 103 -1 ```

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