[identity] Remove parameter causing duplicate target on asan builds

This parameter causes google_auth_provider_unittests to be
added to asan variant builds even though the tests
are not run for those builds, and additionally
causes a duplicate warning to be generated due to
multiple generated ninja targets.  This commit removes
the parameter to remove the warning.

Testing: CQ dryrun, verify duplicate warning removed from
asan variants and google_auth_provider_unittests are still
run for builds such as fuchsia-arm64-debug

Bug: AUTH-216 #done

Change-Id: Idb345687b6e097dd079b7f855999af4ff179b61d
diff --git a/src/identity/bin/google_auth_provider/BUILD.gn b/src/identity/bin/google_auth_provider/BUILD.gn
index ced7704..e8d098f 100644
--- a/src/identity/bin/google_auth_provider/BUILD.gn
+++ b/src/identity/bin/google_auth_provider/BUILD.gn
@@ -51,7 +51,6 @@
 
 source_set("unittests") {
   testonly = true
-  output_name = "google_auth_provider_unittests"
 
   sources = [
     "factory_impl_unittest.cc",