gn2bp: Add `use_nss_certs = false` to gen_desc_json

nss_certs are only used for host net unittestings.
Android.bp is not affected because the tests are not pulled-in yet.

Test: None
Change-Id: Idef23174d1ecd89c2db90318bfb0cf67a4e70145
diff --git a/tools/gn2bp/gen_desc_json.sh b/tools/gn2bp/gen_desc_json.sh
index 1f60eb9..0bd99a9 100755
--- a/tools/gn2bp/gen_desc_json.sh
+++ b/tools/gn2bp/gen_desc_json.sh
@@ -56,6 +56,7 @@
     "is_cronet_build = true"
     "is_debug = false"
     "is_official_build = true"
+    "use_nss_certs = false"
   )
   gn_args+=("target_cpu = \"${1}\"")