Fix UseRequiresApi: Replace @TargetApi with @RequiresApi (facebook#55507)

Summary:
Pull Request resolved: facebook#55507

Replace TargetApi(29) with RequiresApi(29) in BlendModeHelper.kt to fix the
UseRequiresApi lint warning. The RequiresApi annotation from AndroidX properly
propagates the API level requirement to callers, while TargetApi only suppresses
the lint warning locally without providing this safety.

Also updated the import from android.annotation.TargetApi to
androidx.annotation.RequiresApi.

changelog: [internal] internal

Reviewed By: alanleedev

Differential Revision: D92022472

fbshipit-source-id: 775bea90ca96ec28af79a841f9dc36a235eaff85

Author: mdvacca

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/uimanager/BlendModeHelper.kt

@@ -7,10 +7,10 @@
 
 package com.facebook.react.uimanager
 
-import android.annotation.TargetApi
 import android.graphics.BlendMode
 import android.os.Build
 import android.view.ViewGroup
+import androidx.annotation.RequiresApi
 import androidx.core.view.children
 import com.facebook.react.R
 
@@ -20,7 +20,7 @@ import com.facebook.react.R
  * This object provides utilities to convert CSS mix-blend-mode string values into Android's
  * [BlendMode] enumeration and to determine when views need isolated layers for proper blending.
  */
-@TargetApi(29)
+@RequiresApi(29)
 internal object BlendModeHelper {
 
   /**