Updating release notes for 4.2.2.0

Author: foundationdb-ci

docs/sphinx/source/ReleaseNotes.md

@@ -7,6 +7,22 @@ As the [versioning guide](Versioning.md) details, it cannot always be determined
 
 ## 4.2
 
+### 4.2.2.0
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+
+
+**[Full Changelog (4.2.1.0...4.2.2.0)](https://github.com/FoundationDB/fdb-record-layer/compare/4.2.1.0...4.2.2.0)**
+
+#### Mixed Mode Test Results
+
+Mixed mode testing run against the following previous versions:
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+❌`4.0.559.1`, ❌`4.0.559.2`, ❌`4.0.559.3`, ❌`4.0.559.4`, ❌`4.0.559.6`, ❌`4.0.561.0`, ❌`4.0.562.0`, ❌`4.0.564.0`, ❌`4.0.565.0`, ❌`4.0.566.0`, ❌`4.0.567.0`, ❌`4.0.568.0`, ❌`4.0.569.0`, ❌`4.0.570.0`, ❌`4.0.571.0`, ❌`4.0.572.0`, ❌`4.0.573.0`, ❌`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`
+
+[See full test run](https://github.com/FoundationDB/fdb-record-layer/actions/runs/14116508725)
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+
+
 ### 4.2.1.0
 
 <h4> Breaking Changes </h4>