docs: update release notes

Author: ellemouton

docs/release-notes/release-notes-0.20.1.md

@@ -58,6 +58,11 @@
 * [Fix potential sql tx exhaustion 
   issue](https://github.com/lightningnetwork/lnd/pull/10428) in LND which might
   happen when running postgres with a limited number of connections configured.
+ 
+* Fix a bug where [missing edges for own channels could not be added to the
+  graph DB](https://github.com/lightningnetwork/lnd/pull/10443)
+  due to validation checks in the graph Builder that were resurfaced after the
+  graph refactor work.
 
 # New Features