Move CronetInTetheringApexDefaults to //external/cronet

The JNI libs that this target depends on are going to be shimmed on top
of ToT and Stable Cronet. This reduces the number of cross-repo dependencies, making that change simpler (see http://aosp/3507996).

Test: m
Bug: b:396593141
Change-Id: I5e8ab89ea0ebe6a82f006568f30961dcf2f0603e
diff --git a/Tethering/apex/Android.bp b/Tethering/apex/Android.bp
index 2878f79..531489d 100644
--- a/Tethering/apex/Android.bp
+++ b/Tethering/apex/Android.bp
@@ -47,15 +47,6 @@
 // as the above target may have different "enabled" values
 // depending on the branch
 
-apex_defaults {
-    name: "CronetInTetheringApexDefaults",
-    jni_libs: [
-        "cronet_aml_components_cronet_android_cronet",
-        "//external/cronet/third_party/boringssl:libcrypto",
-        "//external/cronet/third_party/boringssl:libssl",
-    ],
-}
-
 apex {
     name: "com.android.tethering",
     defaults: [