Fix gem publishing portion of Jenkinsfile

govuk-jenkinslib does a lot of what we have defined explicitly,
out of the box. For example, gem publishing will automatically
default to the name of the repository, so we don't need to
specify 'REPOSITORY' globally.

Jenkinsfile

@@ -2,50 +2,8 @@
 
 library("govuk")
 
-REPOSITORY = 'govuk_schemas'
-
 node {
-
-  try {
-    stage('Checkout') {
-      checkout scm
-    }
-
-    stage('Clean') {
-      govuk.cleanupGit()
-      govuk.mergeMasterBranch()
-    }
-
-    stage("Set up content schema dependency") {
-      govuk.contentSchemaDependency()
-    }
-
-    stage('Bundle') {
-      echo 'Bundling'
-      sh("bundle install --path ${JENKINS_HOME}/bundles/${JOB_NAME}")
-    }
-
-    stage('Linter') {
-      govuk.lintRuby()
-    }
-
-    stage('Tests') {
-      govuk.setEnvar('RAILS_ENV', 'test')
-      govuk.runTests('spec')
-    }
-
-    if(env.BRANCH_NAME == "master") {
-      stage('Publish Gem') {
-        govuk.publishGem(REPOSITORY, env.BRANCH_NAME)
-      }
-    }
-
-  } catch (e) {
-    currentBuild.result = 'FAILED'
-    step([$class: 'Mailer',
-          notifyEveryUnstableBuild: true,
-          recipients: '[email protected]',
-          sendToIndividuals: true])
-    throw e
-  }
+  govuk.buildProject(
+    rubyLintDiff: false,
+  )
 }