Revert "Add release notes entry"

This reverts commit 9fa53dd3bd.

doc/release-notes.md

@@ -39,49 +39,3 @@ estimate.
 Statistics used to estimate fees and priorities are saved in the
 data directory in the 'fee_estimates.dat' file just before
 program shutdown, and are read in at startup.
-
-Double-Spend Relay and Alerts
-=============================
-VERY IMPORTANT: *It has never been safe, and remains unsafe, to rely*
-*on unconfirmed transactions.*
-
-Relay
------
-When an attempt is seen on the network to spend the same unspent funds
-more than once, it is no longer ignored.  Instead, it is broadcast, to
-serve as an alert.  This broadcast is subject to protections against
-denial-of-service attacks.
-
-Wallets and other bitcoin services should alert their users to
-double-spends that affect them.  Merchants and other users may have
-enough time to withhold goods or services when payment becomes
-uncertain, until confirmation.
-
-Bitcoin Core Wallet Alerts
---------------------------
-The Bitcoin Core wallet now makes respend attempts visible in several
-ways.
-
-If you are online, and a respend affecting one of your wallet
-transactions is seen, a notification is immediately issued to the
-command registered with `-respendnotify=<cmd>`.  Additionally, if
-using the GUI:
- - An alert box is immediately displayed.
- - The affected wallet transaction is highlighted in red until it is
-   confirmed (and it may never be confirmed).
-
-A `respendsobserved` array is added to `gettransaction`, `listtransactions`,
-and `listsinceblock` RPC results.
-
-Warning
--------
-*If you rely on an unconfirmed transaction, these change do VERY*
-*LITTLE to protect you from a malicious double-spend, because:*
-
- - You may learn about the respend too late to avoid doing whatever
-   you were being paid for
- - Using other relay rules, a double-spender can craft his crime to
-   resist broadcast
- - Miners can choose which conflicting spend to confirm, and some
-   miners may not confirmg the first acceptable spend they see
-