Revert of Add field_specs to all metrics in luci-py

client/third_party/infra_libs/ts_mon/config.py

Index: client/third_party/infra_libs/ts_mon/config.py
diff --git a/client/third_party/infra_libs/ts_mon/config.py b/client/third_party/infra_libs/ts_mon/config.py
index 51232b2ee72a36f09673caffa5308706682cc97b..f78d5cea5369a63f3dcec9a098cc2f82e2b81bc0 100644
--- a/client/third_party/infra_libs/ts_mon/config.py
+++ b/client/third_party/infra_libs/ts_mon/config.py
@@ -243,15 +243,14 @@
       project = url.netloc
       topic = url.path.strip('/')
       interface.state.global_monitor = monitors.PubSubMonitor(
-          monitors.CredentialFactory.from_string(credentials), project, topic,
-          use_instrumented_http=True, ca_certs=args.ts_mon_ca_certs)
+          credentials, project, topic, use_instrumented_http=True,
+          ca_certs=args.ts_mon_ca_certs)
     else:
       logging.error('ts_mon monitoring is disabled because credentials are not '
                     'available')
   elif endpoint.startswith('https://'):
     interface.state.global_monitor = monitors.HttpsMonitor(
-        endpoint, monitors.CredentialFactory.from_string(credentials),
-        ca_certs=args.ts_mon_ca_certs)
+        endpoint, credentials, ca_certs=args.ts_mon_ca_certs)
   elif endpoint.lower() == 'none':
     logging.info('ts_mon monitoring has been explicitly disabled')
   else: