[NETD-BPF#23] Make libnetdutils apex_available for tethering module

libconn_for_netd.so in tethering module needs utilities in libnetdutils,
e.g. Status class.

Bug: 202086915
Test: m
Change-Id: Idb7f11d146570972f2467b7faa624f41bd859062

staticlibs/netd/libnetdutils/Android.bp

@@ -36,6 +36,7 @@ cc_library {
     apex_available: [
         "//apex_available:platform",
         "com.android.resolv",
+        "com.android.tethering",
     ],
     min_sdk_version: "29",
 }