Updating release notes for 4.2.2.1 (#3294)

This brings the release notes in from 4.2.2.1 which were committed to
the 4.2.2-release branch.

I tried to cherry-pick 0c0703a but git could not figure out that
4.2.2.1 should be inserted after 4.2.2.0, and so, instead, it
intermingled the notes from 4.2.2.1 with the notes from 4.2.3.0 and
4.2.4.0, so I just copied the notes in.

Co-authored-by: FoundationDB CI <[email protected]>

Author: ScottDugas

docs/sphinx/source/ReleaseNotes.md

@@ -74,6 +74,35 @@ Mixed mode testing run against the following previous versions:
 
 [See full test run](https://github.com/FoundationDB/fdb-record-layer/actions/runs/14134843186)
 
+### 4.2.2.1
+
+<h4> Dependency Updates </h4>
+
+* Downgrade protobuf version back to 3.25.5 and grpc common proto to 2.37.0  - [PR #3288](https://github.com/FoundationDB/fdb-record-layer/pull/3288)
+
+<details>
+<summary>
+
+<h4> Build/Test/Documentation/Style Improvements (click to expand) </h4>
+
+</summary>
+
+* Decrease the number of builds compared during mixed mode to the most recent 10 - [PR #3290](https://github.com/FoundationDB/fdb-record-layer/pull/3290)
+
+</details>
+
+
+**[Full Changelog (4.2.2.0...4.2.2.1)](https://github.com/FoundationDB/fdb-record-layer/compare/4.2.2.0...4.2.2.1)**
+
+#### Mixed Mode Test Results
+
+Mixed mode testing run against the following previous versions:
+
+❌`4.0.574.0`, ❌`4.0.575.0`, ❌`4.1.4.0`, ✅`4.1.5.0`, ✅`4.1.6.0`, ✅`4.1.8.0`, ✅`4.1.9.0`, ✅`4.1.10.0`, ✅`4.2.2.0`, ✅`4.2.3.0`
+
+[See full test run](https://github.com/FoundationDB/fdb-record-layer/actions/runs/14239522793)
+
+
 
 
 ### 4.2.2.0