update changelog titles

Author: katarinasupe

pages/release-notes.mdx

@@ -174,7 +174,7 @@ Memgraph (v2.11.1 and lower).
 
 </Callout>
 
-## Memgraph v2.21.0 and MAGE v1.21.0 - Nov 6, 2024
+## Memgraph v2.21.0 - Nov 6, 2024
 
 {<h3> New features and improvements </h3>}
 
@@ -249,7 +249,7 @@ labeled with `jepsen`).
   now stopped before thread pool in RPC client.
   [#2447](https://github.com/memgraph/memgraph/pull/2447)
 
-### MAGE v1.21.0
+## MAGE v1.21.0 - Nov 6, 2024
 
 {<h3> New features and improvements </h3>}