[kotlinp] Minor. Remove unnecessary -opt-in=kotlin.RequiresOptIn

This opt-in is no more required in :tools:kotlinp

^KT-62340

libraries/tools/kotlinp/build.gradle.kts

@@ -1,5 +1,4 @@
 import com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar
-import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
 
 description = "kotlinp"
 
@@ -62,9 +61,3 @@ tasks {
         dependsOn(rootProject.tasks.named("dist"))
     }
 }
-
-tasks.withType<KotlinCompile> {
-    kotlinOptions {
-        freeCompilerArgs += listOf("-opt-in=kotlin.RequiresOptIn")
-    }
-}