chore: change nimbus sidecar URL default port to 8001 (#3438)

.env-dist

@@ -155,4 +155,4 @@ GCP_PUBSUB_SUBSCRIPTION_NAME=
 
 # Randomly-generated UUIDv5 namespace, until/unless we are approved to use FxA UID for Nimbus User ID.
 NIMBUS_UUID_NAMESPACE=00000000-0000-0000-0000-000000000000
-NIMBUS_SIDECAR_URL=http://localhost:6060
+NIMBUS_SIDECAR_URL=http://localhost:8001