Use `.text-center` class instead of text-align prop

app/assets/stylesheets/pages/settings.scss

@@ -67,7 +67,6 @@
 
   .loading-metrics,
   .empty-metrics {
-    text-align: center;
     padding: 30px 10px;
 
     p,

app/views/projects/services/prometheus/_show.html.haml

@@ -17,10 +17,10 @@
           Monitored
           %span.badge.js-monitored-count 0
       .panel-body
-        .loading-metrics.js-loading-metrics
+        .loading-metrics.text-center.js-loading-metrics
           = icon('spinner spin 3x', class: 'metrics-load-spinner')
           %p Finding and configuring metrics...
-        .empty-metrics.hidden.js-empty-metrics
+        .empty-metrics.text-center.hidden.js-empty-metrics
           = custom_icon('icon_empty_metrics')
           %p No metrics are being monitored. To start monitoring, deploy to an environment.
           = link_to project_environments_path(@project), title: 'View environments', class: 'btn btn-success' do