Add comments to network permission declaration

Bug: 223649084
Test: m
Ignore-AOSP-First: Address the comment for the previous change to tm-dev.
Change-Id: Ia75440b52eccc75babac739fc28d2589d59d05bd
diff --git a/AndroidManifest.xml b/AndroidManifest.xml
index b27c78f..ad6c2b5 100644
--- a/AndroidManifest.xml
+++ b/AndroidManifest.xml
@@ -23,6 +23,7 @@
   android:versionName="s_aml_319999900"
   coreApp="true"
 >
+    <!--- Defines the MAINLINE_NETWORK_STACK permission used by the networkstack process. -->
     <permission android:name="android.permission.MAINLINE_NETWORK_STACK"
                 android:protectionLevel="signature"/>
     <!-- Permissions must be defined here, and not in the base manifest, as the network stack