disable pageLoadMetrics job, it's gotten really flaky

(cherry picked from commit 02a3800)

Author: spalger

Jenkinsfile

@@ -41,7 +41,7 @@ kibanaPipeline(timeoutMinutes: 155, checkPrChanges: true) {
             'xpack-ciGroup9': kibanaPipeline.xpackCiGroupProcess(9),
             'xpack-ciGroup10': kibanaPipeline.xpackCiGroupProcess(10),
             'xpack-accessibility': kibanaPipeline.functionalTestProcess('xpack-accessibility', './test/scripts/jenkins_xpack_accessibility.sh'),
-            'xpack-pageLoadMetrics': kibanaPipeline.functionalTestProcess('xpack-pageLoadMetrics', './test/scripts/jenkins_xpack_page_load_metrics.sh'),
+            // 'xpack-pageLoadMetrics': kibanaPipeline.functionalTestProcess('xpack-pageLoadMetrics', './test/scripts/jenkins_xpack_page_load_metrics.sh'),
             'xpack-securitySolutionCypress': { processNumber ->
               whenChanged(['x-pack/plugins/security_solution/', 'x-pack/test/security_solution_cypress/']) {
                 kibanaPipeline.functionalTestProcess('xpack-securitySolutionCypress', './test/scripts/jenkins_security_solution_cypress.sh')(processNumber)