remove optional key

don't make hmac optional by default, as other git providers still use
it.
instead it will be added in the versionStream

Author: dali546

charts/lighthouse-webui-plugin/values.yaml

@@ -25,7 +25,6 @@ secrets:
       secretKeyRef:
         name: lighthouse-hmac-token
         key: hmac
-        optional: true
 
 image:
   repository: ghcr.io/jenkins-x/lighthouse-webui-plugin