Add 'float_job' dimension to target:probe_ssl_cert_expiry:days

Otherwise it's impossible to figure out what the SSLCertificateAboutToExpire
alerts are referring to (everything is about the "health" probe).

roles/float-infra-prometheus/templates/rules/rules_ssl_probes.conf.yml

@@ -2,7 +2,7 @@ groups:
   - name: roles/float-infra-prometheus/templates/rules/rules_ssl_probes.conf
     rules:
       - record: target:probe_ssl_cert_expiry:days
-        expr: ((min(probe_ssl_earliest_cert_expiry) by (probe,host)) - time()) / 86400
+        expr: ((min(probe_ssl_earliest_cert_expiry) by (float_job,probe,host)) - time()) / 86400
 
       - record: service_credentials_expiration_time:days
         expr: ((min(service_credentials_expiration_time) by (name,float_service)) - time()) / 86400