docs: prepare v0.51.0

A large release with lots of changes I am looking forward to. Sorry for the long release cadence.

Anything folks would like to see included that is not yet in `master`? As usual I would like to only block on bug fixes.

Pull-Request: #3491.

protocols/autonat/CHANGELOG.md

@@ -1,4 +1,4 @@
-# 0.10.0 [unreleased]
+# 0.10.0
 
 - Update to `libp2p-core` `v0.39.0`.
 

protocols/dcutr/CHANGELOG.md

@@ -1,4 +1,4 @@
-# 0.9.0 [unreleased]
+# 0.9.0
 
 - Update to `libp2p-core` `v0.39.0`.
 

protocols/floodsub/CHANGELOG.md

@@ -1,4 +1,4 @@
-# 0.42.0 [unreleased]
+# 0.42.0
 
 - Update to `libp2p-core` `v0.39.0`.
 

protocols/gossipsub/CHANGELOG.md

@@ -1,4 +1,4 @@
-# 0.44.0 [unreleased]
+# 0.44.0
 
 - Update to `prometheus-client` `v0.19.0`. See [PR 3207].
 

protocols/identify/CHANGELOG.md

@@ -1,4 +1,4 @@
-# 0.42.0 [unreleased]
+# 0.42.0
 
 - Update to `libp2p-core` `v0.39.0`.
 

protocols/kad/CHANGELOG.md

@@ -1,4 +1,4 @@
-# 0.43.0 [unreleased]
+# 0.43.0
 
 - Update to `libp2p-core` `v0.39.0`.
 

protocols/mdns/CHANGELOG.md

@@ -1,4 +1,4 @@
-# 0.43.0 [unreleased]
+# 0.43.0
 
 - Update to `libp2p-core` `v0.39.0`.
 

protocols/ping/CHANGELOG.md

@@ -1,4 +1,4 @@
-# 0.42.0 [unreleased]
+# 0.42.0
 
 - Update to `libp2p-core` `v0.39.0`.
 

protocols/relay/CHANGELOG.md

@@ -1,4 +1,4 @@
-# 0.15.0 [unreleased]
+# 0.15.0
 
 - Rename types as per [discussion 2174].
   `Relay` has been renamed to `Behaviour`.

protocols/rendezvous/CHANGELOG.md

@@ -1,4 +1,4 @@
-# 0.12.0 [unreleased]
+# 0.12.0
 
 - Update to `libp2p-core` `v0.39.0`.
 

protocols/request-response/CHANGELOG.md

@@ -1,4 +1,4 @@
-# 0.24.0 [unreleased]
+# 0.24.0
 
 - Update to `libp2p-core` `v0.39.0`.