Fix UnsafeDereference: Remove !! operators in FpsView (#56115)

Summary:
Pull Request resolved: #56115

Fixed UnsafeDereference lint warnings in FpsView.kt.

Changed the `reactContext` parameter type from `ReactContext?` to `ReactContext` since the superclass FrameLayout requires a non-null Context anyway. This eliminates the need for !! operators.

changelog: [internal] internal

Reviewed By: alanleedev

Differential Revision: D96784792

fbshipit-source-id: 7409bba7037775d24ddc83fa7981a5ad7aa86fc7

Author: mdvacca

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/devsupport/FpsView.kt

@@ -23,15 +23,15 @@ import java.util.Locale
  *
  * NB: Requires API 16 for use of FpsDebugFrameCallback.
  */
-internal class FpsView(reactContext: ReactContext?) : FrameLayout(reactContext!!) {
+internal class FpsView(reactContext: ReactContext) : FrameLayout(reactContext) {
   private val textView: TextView
   private val frameCallback: FpsDebugFrameCallback
   private val fpsMonitorRunnable: FPSMonitorRunnable
 
   init {
     inflate(reactContext, R.layout.fps_view, this)
     textView = findViewById<View>(R.id.fps_text) as TextView
-    frameCallback = FpsDebugFrameCallback(reactContext!!)
+    frameCallback = FpsDebugFrameCallback(reactContext)
     fpsMonitorRunnable = FPSMonitorRunnable()
     setCurrentFPS(0.0, 0.0, 0, 0, frameCallback.isRunningOnFabric)
   }