Stop Tethering requiring NetworkStack

It leads to complexity when Tethering is overridden, because the
required attribute must be duplicated for all the variants.

Require NetworkStack be explicitly installed instead.

Bug: 242509786
Test: m
Change-Id: Ideaecf88418901e2c86271166be24f6b7e498a20
diff --git a/Tethering/Android.bp b/Tethering/Android.bp
index b88ec7f..23ce1a4 100644
--- a/Tethering/Android.bp
+++ b/Tethering/Android.bp
@@ -195,11 +195,7 @@
     certificate: "networkstack",
     manifest: "AndroidManifest.xml",
     use_embedded_native_libs: true,
-    // The network stack *must* be included to ensure security of the device
-    required: [
-        "NetworkStack",
-        "privapp_allowlist_com.android.tethering",
-    ],
+    required: ["privapp_allowlist_com.android.tethering"],
     apex_available: ["com.android.tethering"],
     lint: { strict_updatability_linting: true },
 }
@@ -215,11 +211,7 @@
     certificate: "networkstack",
     manifest: "AndroidManifest.xml",
     use_embedded_native_libs: true,
-    // The network stack *must* be included to ensure security of the device
-    required: [
-        "NetworkStackNext",
-        "privapp_allowlist_com.android.tethering",
-    ],
+    required: ["privapp_allowlist_com.android.tethering"],
     apex_available: ["com.android.tethering"],
     lint: { strict_updatability_linting: true },
 }