Fix insecure SAML configuration

Currently, the .Values.anchoreGlobal.saml.secret is accidentally hard-coded to anchore-certs. Anchore handles this as a value (not as a secretName)

https://repo1.dso.mil/platform-one/big-bang/apps/security-tools/anchore-enterprise/-/blob/main/chart/values.yaml#L254

We could supply a secret or tls certs but it would be easiest to simply allow the user to specify this value or generate a random value

ALSO TO-DO:

• put a conditional on the anchore-certs secret?