Fix cloud build and readme (tensorflow#2555)

* fix cloud function error and updated readme

* updated readme

Author: pyu10055

tfjs-converter/cloudbuild_nightly.yml

@@ -23,8 +23,6 @@ steps:
 
 secrets:
 - kmsKeyName: projects/learnjs-174218/locations/global/keyRings/tfjs/cryptoKeys/enc
-  secretEnv:
-    BROWSERSTACK_KEY: CiQAkwyoIW0LcnxymzotLwaH4udVTQFBEN4AEA5CA+a3+yflL2ASPQAD8BdZnGARf78MhH5T9rQqyz9HNODwVjVIj64CTkFlUCGrP1B2HX9LXHWHLmtKutEGTeFFX9XhuBzNExA=
 timeout: 1800s
 logsBucket: 'gs://tfjs-build-logs'
 substitutions:

tfjs-converter/scripts/cloud_funcs/README.md

@@ -6,9 +6,9 @@ You can also trigger the function manually via the Cloud UI.
 
 Command to re-deploy:
 ```sh
-gcloud functions deploy converter_pip_nightly_test \
+gcloud functions deploy converter_python_nightly \
   --runtime nodejs8 \
-  --trigger-topic nightly
+  --trigger-topic converter_python_nightly
 ```
 
 ### The pipeline