Update Kotlin core dependencies to v1.7.21 (#1558)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

diktat-gradle-plugin/build.gradle.kts

@@ -3,7 +3,7 @@ import org.gradle.nativeplatform.platform.internal.DefaultNativePlatform.getCurr
 
 plugins {
     `java-gradle-plugin`
-    kotlin("jvm") version "1.7.20"
+    kotlin("jvm") version "1.7.21"
     jacoco
     id("pl.droidsonroids.jacoco.testkit") version "1.0.9"
     id("org.gradle.test-retry") version "1.4.1"

examples/gradle-kotlin-dsl-multiproject/build.gradle.kts

@@ -1,7 +1,7 @@
 import org.cqfn.diktat.plugin.gradle.DiktatExtension
 
 plugins {
-    kotlin("jvm") version "1.7.20"
+    kotlin("jvm") version "1.7.21"
     id("org.cqfn.diktat.diktat-gradle-plugin")
 }
 

pom.xml

@@ -42,7 +42,7 @@
         <maven.compiler.source>1.8</maven.compiler.source>
         <maven.compiler.target>1.8</maven.compiler.target>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-        <kotlin.version>1.7.20</kotlin.version>
+        <kotlin.version>1.7.21</kotlin.version>
         <kotlin.compiler.incremental>true</kotlin.compiler.incremental>
         <kotlin.code.style>official</kotlin.code.style>
         <kotlinx.serialization.version>1.4.1</kotlinx.serialization.version>