Add createmultisig and addmultisigaddress warnings release note

doc/release-notes-23113.md

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+Notable changes
+===============
+
+Updated RPCs
+------------
+
+- Both `createmultisig` and `addmultisigaddress` now include a `warnings`
+field, which will show a warning if a non-legacy address type is requested
+when using uncompressed public keys.