Fix oppia#5404: Migrate away from onBackPressed for RevisionCardActiv…

…ity (oppia#5548)

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Fixes oppia#5404 

This PR migrates deprecated `onBackPressed `usage to
`OnBackPressedDispatcher` callback in the RevisonCardActivity and
RevisionCardActivityPresenter.
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app/src/main/java/org/oppia/android/app/topic/revisioncard/RevisionCardActivity.kt

@@ -3,6 +3,7 @@ package org.oppia.android.app.topic.revisioncard
 import android.content.Context
 import android.content.Intent
 import android.os.Bundle
+import androidx.activity.OnBackPressedCallback
 import org.oppia.android.app.activity.ActivityComponentImpl
 import org.oppia.android.app.activity.InjectableAutoLocalizedAppCompatActivity
 import org.oppia.android.app.model.ProfileId
@@ -56,6 +57,15 @@ class RevisionCardActivity :
         subtopicListSize
       )
     }
+    onBackPressedDispatcher.addCallback(
+      this,
+      object : OnBackPressedCallback(/* enabled = */ true) {
+        override fun handleOnBackPressed() {
+          revisionCardActivityPresenter.setReadingTextSizeMedium()
+          onReturnToTopicRequested()
+        }
+      }
+    )
   }
 
   override fun handleOnOptionsItemSelected(itemId: Int) {
@@ -115,13 +125,6 @@ class RevisionCardActivity :
     revisionCardActivityPresenter.dismissConceptCard()
   }
 
-  // TODO(#5404): Migrate to a back pressed dispatcher.
-  @Deprecated("Deprecated in Java")
-  override fun onBackPressed() {
-    revisionCardActivityPresenter.setReadingTextSizeMedium()
-    onReturnToTopicRequested()
-  }
-
   override fun onDefaultFontSizeLoaded(readingTextSize: ReadingTextSize) {
     revisionCardActivityPresenter.loadRevisionCardFragment(readingTextSize)
   }

app/src/main/java/org/oppia/android/app/topic/revisioncard/RevisionCardActivityPresenter.kt

@@ -83,8 +83,7 @@ class RevisionCardActivityPresenter @Inject constructor(
     binding.revisionCardToolbar.setNavigationOnClickListener {
       (activity as ReturnToTopicClickListener).onReturnToTopicRequested()
       fontScaleConfigurationUtil.adjustFontScale(activity, ReadingTextSize.MEDIUM_TEXT_SIZE)
-      @Suppress("DEPRECATION") // TODO(#5404): Migrate to a back pressed dispatcher.
-      activity.onBackPressed()
+      activity.onBackPressedDispatcher.onBackPressed()
     }
     if (!accessibilityService.isScreenReaderEnabled()) {
       binding.revisionCardToolbarTitle.setOnClickListener {