docs: update release notes

docs/release-notes/release-notes-0.14.3.md

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+# Release Notes
+
+## Bug fixes
+
+* The REST proxy (`grpc-gateway` library) had a fallback that redirected `POST`
+  requests to another endpoint _with the same URI_ if no endpoint for `POST` was
+  registered. [This default behavior was turned
+  off](https://github.com/lightningnetwork/lnd/pull/6359), enabling strict
+  HTTP method matching.
+
+# Contributors (Alphabetical Order)
+
+* Oliver Gugger