ui: refactor AddTunnelsSheet's selection communication

Signed-off-by: Harsh Shandilya <me@msfjarvis.dev>

ui/src/main/java/com/wireguard/android/util/Extensions.kt

@@ -8,7 +8,6 @@ package com.wireguard.android.util
 import android.content.Context
 import android.util.TypedValue
 import androidx.annotation.AttrRes
-import androidx.fragment.app.Fragment
 import androidx.lifecycle.lifecycleScope
 import androidx.preference.Preference
 import com.wireguard.android.Application
@@ -21,10 +20,6 @@ fun Context.resolveAttribute(@AttrRes attrRes: Int): Int {
     return typedValue.data
 }
 
-fun Fragment.requireTargetFragment(): Fragment {
-    return requireNotNull(targetFragment) { "A target fragment should always be set for $this" }
-}
-
 val Any.applicationScope: CoroutineScope
     get() = Application.getCoroutineScope()