Updating release notes for 4.8.4.0

Author: foundationdb-ci

docs/sphinx/source/ReleaseNotes.md

@@ -7,6 +7,28 @@ As the [versioning guide](Versioning.md) details, it cannot always be determined
 
 ## 4.8
 
+### 4.8.4.0
+
+<h4> New Features </h4>
+
+* Protobuf compliant translation for supporting richer identifiers for tables and columns - [PR #3696](https://github.com/FoundationDB/fdb-record-layer/pull/3696)
+<h4> Performance Improvements </h4>
+
+* Reactivate amortization of plan generation of functions. - [PR #3595](https://github.com/FoundationDB/fdb-record-layer/pull/3595)
+
+
+**[Full Changelog (4.8.3.0...4.8.4.0)](https://github.com/FoundationDB/fdb-record-layer/compare/4.8.3.0...4.8.4.0)**
+
+#### Mixed Mode Test Results
+
+Mixed mode testing run against the following previous versions:
+
+❌`4.6.2.0`, ❌`4.6.3.0`, ❌`4.6.4.0`, ❌`4.6.5.0`, ❌`4.7.1.0`, ❌`4.7.2.0`, ✅`4.7.3.0`, ✅`4.8.1.0`, ✅`4.8.2.0`, ✅`4.8.3.0`
+
+[See full test run](https://github.com/FoundationDB/fdb-record-layer/actions/runs/18946501767)
+
+
+
 ### 4.8.3.0
 
 <h4> New Features </h4>