Only run Foreman testing on a single Ruby version

This makes it easier switch and configure via variables, but also makes
it consistent with generating the source.

Author: ekohl

theforeman.org/pipelines/release/source/foreman.groovy

@@ -9,6 +9,7 @@ pipeline {
     }
 
     environment {
+        RUBY_VER = '2.7.6'
         BUNDLE_WITHOUT = 'development'
         RAILS_ENV = railsEnvForTask(TASK)
         DATABASE_URL = databaseUrlForTask(TASK)
@@ -20,10 +21,6 @@ pipeline {
             matrix {
                 agent { label 'fast' }
                 axes {
-                    axis {
-                        name 'RUBY_VER'
-                        values '2.7.6'
-                    }
                     axis {
                         name 'TASK'
                         values 'jenkins:unit', 'jenkins:integration', 'assets:precompile'
@@ -79,7 +76,7 @@ pipeline {
                     git url: git_url, branch: git_ref
                 }
                 script {
-                    sourcefile_paths = generate_sourcefiles(project_name: project_name, source_type: source_type)
+                    sourcefile_paths = generate_sourcefiles(project_name: project_name, source_type: source_type, ruby_version: RUBY_VER)
                 }
             }
         }