JAVA-41701 Upgrade main Kotlin version

Author: anastasiosioannidis

pom.xml

@@ -765,7 +765,7 @@
     </profiles>
 
     <properties>
-        <kotlin.version>2.0.20</kotlin.version>
+        <kotlin.version>2.0.21</kotlin.version>
         <kotlinx.version>1.7.1</kotlinx.version>
         <ktlint-cli.version>1.0.1</ktlint-cli.version>