Remove old opt-in for RequiresOptIn (#3167)

As of Kotlin 1.7 the opt-in feature is now stable and does not need an explicit declaration.

https://kotlinlang.org/docs/whatsnew17.html#stable-opt-in-requirements

app/build.gradle

@@ -91,9 +91,6 @@ android {
             enableSplit = false
         }
     }
-    kotlinOptions {
-        freeCompilerArgs += "-opt-in=kotlin.RequiresOptIn"
-    }
     dependenciesInfo {
         includeInApk false
         includeInBundle false