Notes about Berlin upgrade (hyperledger#1988)

Signed-off-by: Tim Beiko <t.beiko23@gmail.com>

Co-authored-by: Danno Ferrin <danno.ferrin@gmail.com>

CHANGELOG.md

@@ -2,7 +2,18 @@
 
 ## 21.1.1
 
+### Berlin Network Upgrade
+
+This release contains the activation blocks for Berlin across all supported testnets and the Ethereum mainnet. They are: 
+  * Ropsten 9_812_189 (10 Mar 2021)
+  * Goerli 4_460_644 (17 Mar 2021)
+  * Rinkeby 8_290_928 (24 Mar 2021)
+  * Ethereum 12_244_000 (14 Apr 2021)
+
+**Important note: the 21.1.0 release contains an outdated version of the Berlin network upgrade. If you are using Besu on public Ethereum networks, you must upgrade to 21.1.1.**
+
 ### Additions and Improvements
+* Removed EIP-2315 from the Berlin network upgrade [\#1983](https://github.com/hyperledger/besu/pull/1983)
 * Added `besu_transaction_pool_transactions` to the reported metrics, counting the mempool size [\#1869](https://github.com/hyperledger/besu/pull/1869)
 * Distributions and maven artifacts have been moved off of bintray [\#1886](https://github.com/hyperledger/besu/pull/1886)
 * admin_peers json RPC response now includes the remote nodes enode URL
@@ -20,6 +31,8 @@
 
 ## 21.1.0
 
+**Important note: this release contains an outdated version of the Berlin network upgrade, which was changed on March 5, 2021 ([link](https://github.com/ethereum/pm/issues/263#issuecomment-791473406)). If you are using Besu on public Ethereum networks, you must upgrade to 21.1.1.**
+
 ## 21.1.0 Features
 
 Features added between 20.10.0 to 21.1.0 include:
@@ -89,7 +102,9 @@ sha256: `e4c8fe4007e3e5f7f2528cbf1eeb5457caf06536c974a6ff4305035ff5724476`
 
 
 ### Download link
-https://dl.bintray.com/hyperledger-org/besu-repo/besu-21.1.0-RC1.zip
+
+Link removed because this release contains an outdated version of the Berlin network upgrade, which was changed on March 5, 2021 ([link](https://github.com/ethereum/pm/issues/263#issuecomment-791473406)). If you are using Besu on public Ethereum networks, you must upgrade to 21.1.1. sha256 hash left for reference. 
+
 sha256: `b0fe3942052b8fd43fc3025a298a6c701f9edae2e100f0c563a1c5a4ceef71f1`
 
 ## 20.10.4