[fenix] Fix for https://github.com/mozilla-mobile/fenix/issues/8024 - Provide activity class for the migration's service notification content intent.

app/src/migration/java/org/mozilla/fenix/MigrationService.kt

@@ -7,6 +7,7 @@ package org.mozilla.fenix
 import mozilla.components.support.migration.AbstractMigrationService
 import mozilla.components.support.migration.state.MigrationStore
 import org.mozilla.fenix.ext.components
+import org.mozilla.fenix.migration.MigrationProgressActivity
 
 /**
  * Background service for running the migration from legacy Firefox for Android (Fennec).
@@ -14,4 +15,5 @@ import org.mozilla.fenix.ext.components
 class MigrationService : AbstractMigrationService() {
     override val migrator by lazy { getMigratorFromApplication() }
     override val store: MigrationStore by lazy { components.migrationStore }
+    override val migrationActivity = MigrationProgressActivity::class.java
 }