Bump kotlin.version from 1.5.31 to 1.6.0

Bumps `kotlin.version` from 1.5.31 to 1.6.0.

Updates `kotlin-maven-allopen` from 1.5.31 to 1.6.0

Updates `kotlin-maven-plugin` from 1.5.31 to 1.6.0

---
updated-dependencies:
- dependency-name: org.jetbrains.kotlin:kotlin-maven-allopen
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: org.jetbrains.kotlin:kotlin-maven-plugin
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

mybatis-spring-boot-samples/mybatis-spring-boot-sample-kotlin/pom.xml

@@ -28,7 +28,7 @@
   <name>mybatis-spring-boot-sample-kotlin</name>
   <properties>
     <module.name>org.mybatis.spring.boot.sample.kotlin</module.name>
-    <kotlin.version>1.5.31</kotlin.version>
+    <kotlin.version>1.6.0</kotlin.version>
     <java.version>1.8</java.version>
   </properties>
   <dependencies>