[Gradle] Remove deprecated experimental annotation methods & properties

#KT-47763 Fixed

libraries/tools/kotlin-gradle-plugin-api/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/LanguageSettingsBuilder.kt

@@ -18,11 +18,5 @@ interface LanguageSettingsBuilder : LanguageSettings {
 
     override val enabledLanguageFeatures: Set<String>
 
-    @Deprecated("Unsupported and will be removed in next major releases", replaceWith = ReplaceWith("optIn(name)"))
-    fun useExperimentalAnnotation(name: String)
-
     fun optIn(annotationName: String)
-
-    @Deprecated("Unsupported and will be removed in next major releases", replaceWith = ReplaceWith("optInAnnotationsInUse"))
-    override val experimentalAnnotationsInUse: Set<String>
 }