docs: add release note for lncli unlock --stdin EOF fix

Author: 0xfandom

docs/release-notes/release-notes-0.22.0.md

@@ -21,6 +21,10 @@
 
 # Bug Fixes
 
+* [`lncli unlock --stdin`](https://github.com/lightningnetwork/lnd/pull/PR_NUMBER)
+  now reads the password until EOF instead of stopping at the first newline,
+  so passwords containing embedded newline bytes are accepted.
+
 # New Features
 
 ## Functional Enhancements