Update changelog for 4.12.1 release

Author: adutra

changelog/README.md

@@ -2,7 +2,7 @@
 
 <!-- Note: contrary to 3.x, insert new entries *first* in their section -->
 
-### 4.12.1 (in progress)
+### 4.12.1
 
 Merged from 4.11.x:
 
@@ -25,7 +25,7 @@ Merged from 4.11.x:
 - [bug] JAVA-2943: Prevent session leak with wrong keyspace name
 - [bug] JAVA-2938: OverloadedException message is misleading
 
-### 4.11.3 (in progress)
+### 4.11.3
 
 - [bug] JAVA-2949: Provide mapper support for CompletionStage<Stream<T>>
 - [bug] JAVA-2950: Remove reference to Reflection class from DependencyCheck