Wizard: upgrade Gradle version to 6.3

#KT-37932 fixed

libraries/tools/new-project-wizard/new-project-wizard-cli/tests/org/jetbrains/kotlin/tools/projectWizard/cli/testUtils.kt

@@ -71,16 +71,14 @@ enum class BuildSystem(
         additionalFileNames = listOf("settings.gradle.kts"),
         yaml = """buildSystem:
                             type: GradleKotlinDsl
-                            gradle:
-                              version: 5.4.1""".trimIndent()
+                            """.trimIndent()
     ),
     GRADLE_GROOVY_DSL(
         buildFileName = "build.gradle",
         additionalFileNames = listOf("settings.gradle"),
         yaml = """buildSystem:
                             type: GradleGroovyDsl
-                            gradle:
-                              version: 5.4.1""".trimIndent()
+                            """.trimIndent()
     ),
     MAVEN(
         buildFileName = "pom.xml",

libraries/tools/new-project-wizard/src/org/jetbrains/kotlin/tools/projectWizard/Versions.kt

@@ -9,6 +9,7 @@ import org.jetbrains.kotlin.tools.projectWizard.settings.version.Version
 
 object Versions {
     val KOTLIN = version("1.3.70")
+    val GRADLE = version("6.3")
 
     object GradlePlugins {
         val ANDROID = version("3.5.2")

libraries/tools/new-project-wizard/src/org/jetbrains/kotlin/tools/projectWizard/plugins/buildSystem/gradle/GradlePlugin.kt

@@ -1,6 +1,7 @@
 package org.jetbrains.kotlin.tools.projectWizard.plugins.buildSystem.gradle
 
 
+import org.jetbrains.kotlin.tools.projectWizard.Versions
 import org.jetbrains.kotlin.tools.projectWizard.core.*
 import org.jetbrains.kotlin.tools.projectWizard.core.entity.settings.reference
 import org.jetbrains.kotlin.tools.projectWizard.core.service.FileSystemWizardService
@@ -24,13 +25,6 @@ import org.jetbrains.kotlin.tools.projectWizard.templates.FileTemplateDescriptor
 
 
 abstract class GradlePlugin(context: Context) : BuildSystemPlugin(context) {
-    val version by versionSetting("Gradle Version", GenerationPhase.FIRST_STEP) {
-        defaultValue = value(defaultVersions.first())
-        isAvailable = isGradle
-    }
-
-    val gradleVersions by property<List<Version>>(emptyList())
-
     val gradleProperties by listProperty(
         "kotlin.code.style" to "official"
     )
@@ -94,7 +88,7 @@ abstract class GradlePlugin(context: Context) : BuildSystemPlugin(context) {
                     ),
                     StructurePlugin::projectPath.reference.settingValue,
                     mapOf(
-                        "version" to GradlePlugin::version.reference.settingValue.toString()
+                        "version" to Versions.GRADLE
                     )
                 )
             )
@@ -131,11 +125,6 @@ abstract class GradlePlugin(context: Context) : BuildSystemPlugin(context) {
             )
         }
     }
-
-    companion object {
-        // TODO update default versions
-        private val defaultVersions = listOf("5.5.1").map(Version.Companion::fromString)
-    }
 }
 
 val Reader.settingsGradleBuildFileData