Upgrade to Kotlin 1.6.10

Closes gh-10350

config/spring-security-config.gradle

@@ -113,8 +113,8 @@ rncToXsd {
 
 tasks.withType(KotlinCompile).configureEach {
 	kotlinOptions {
-		languageVersion = "1.3"
+		languageVersion = "1.6"
-		apiVersion = "1.3"
+		apiVersion = "1.6"
 		freeCompilerArgs = ["-Xjsr305=strict", "-Xsuppress-version-warnings"]
 		jvmTarget = "11"
 	}

gradle.properties

@@ -4,7 +4,7 @@ springBootVersion=2.4.2
 springFrameworkVersion=6.0.0-M1
 openSamlVersion=3.4.6
 version=6.0.0-SNAPSHOT
-kotlinVersion=1.5.31
+kotlinVersion=1.6.10
 samplesBranch=6.0.x
 org.gradle.jvmargs=-Xmx3g -XX:+HeapDumpOnOutOfMemoryError
 org.gradle.parallel=true