PPA Prod adjust how secrets are handled (#219)

* handle secrets differently

* removed secret params from main method signature

* simpler adjustment to read values from env vars, still use @click & specify the envvar name for the couple of values

jobs/dap-collector-ppa-prod/dap_collector_ppa_prod/main.py

@@ -252,11 +252,13 @@ def store_data(results, bqclient, table_id):
 )
 @click.option(
     "--auth-token",
+    envvar='AUTH_TOKEN',
     help="HTTP bearer token to authenticate to the leader",
     required=True,
 )
 @click.option(
     "--hpke-private-key",
+    envvar='HPKE_PRIVATE_KEY',
     help="The private key used to decrypt shares from the leader and helper.",
     required=True,
 )