Adjusts variables table width

- The table width was shrinking with smaller variable names

app/assets/stylesheets/pages/builds.scss

@@ -237,6 +237,7 @@
   .trigger-build-variables {
     margin: 0;
     overflow-x: auto;
+    width: 100%;
     -ms-overflow-style: scrollbar;
     -webkit-overflow-scrolling: touch;
   }