Ignore reporting signon permission token expiry metrics

Tokens for the signon permissions users are automatically rotated once
they expire, so we don't need to trigger alerts for them.

lib/collectors/global_prometheus_collector.rb

@@ -25,8 +25,11 @@ def metrics
     def token_expiry_info
       # Cache metric to prevent needless expensive calls to the database
       Rails.cache.fetch("token_expiry_info", expires_in: 1.hour) do
-        ApiUser.all.flat_map do |user|
-          user.authorisations.where(revoked_at: nil).map do |token|
+        ApiUser
+          .where.not(email: SSOPushCredential::USER_EMAIL)
+          .flat_map do |user|
+          user.authorisations
+            .where(revoked_at: nil).map do |token|
             {
               expires_at: token.expires_at.to_i,
               api_user: user.email,