Merge #20185: doc: Merge release notes

fa38093 doc: Merge release notes (MarcoFalke)

Pull request description:

  Now that all features are merged, open release notes editing at the wiki

  https://github.com/bitcoin-core/bitcoin-devwiki/wiki/0.21.0-Release-Notes-Draft

ACKs for top commit:
  fanquake:
    ACK fa38093

Tree-SHA512: ced161a2fcb0366a77a05b020c8dd65a0cf0a0de17b8260bbca9b5833ed370f92b1b81116bfc59b83380bf28b55d8963c628cf13a0cad603e5c823341b446065

Author: fanquake

doc/release-notes-19988.md

@@ -82,6 +82,14 @@ P2P and network changes
   node using P2P relay. This version reduces the initial broadcast guarantees
   for wallet transactions submitted via P2P to a node running the wallet. (#18038)
 
+- The size of the set of transactions that peers have announced and we consider
+  for requests has been reduced from 100000 to 5000 (per peer), and further
+  announcements will be ignored when that limit is reached. If you need to dump
+  (very) large batches of transactions, exceptions can be made for trusted
+  peers using the "relay" network permission. For localhost for example it can
+  be enabled using the command line option `[email protected]`.
+  (#19988)
+
 - The Tor onion service that is automatically created by setting the
   `-listenonion` configuration parameter will now be created as a Tor v3 service
   instead of Tor v2. The private key that was used for Tor v2 (if any) will be