[android_alarm_manager] fix AndroidManifest.xml for android lint issue "XML tag has empty body" (#3288)

Author: rh-id

packages/android_alarm_manager/README.md

@@ -36,7 +36,7 @@ Next, within the `<application></application>` tags, add:
     android:name="io.flutter.plugins.androidalarmmanager.RebootBroadcastReceiver"
     android:enabled="false">
     <intent-filter>
-        <action android:name="android.intent.action.BOOT_COMPLETED"></action>
+        <action android:name="android.intent.action.BOOT_COMPLETED"/>
     </intent-filter>
 </receiver>
 

packages/android_alarm_manager/example/android/app/src/main/AndroidManifest.xml

@@ -41,7 +41,7 @@
             android:name="io.flutter.plugins.androidalarmmanager.RebootBroadcastReceiver"
             android:enabled="false">
             <intent-filter>
-                <action android:name="android.intent.action.BOOT_COMPLETED"></action>
+                <action android:name="android.intent.action.BOOT_COMPLETED"/>
             </intent-filter>
         </receiver>
         <meta-data