Add text-secondary colors back

app/assets/stylesheets/bootstrap_migration.scss

@@ -70,6 +70,11 @@ table {
   }
 }
+.text-secondary {
+  // Override Bootstrap's light secondary color
+  // We have to use !important because bootstrap has that set as well
+  color: $gl-text-color-secondary !important;
+}
 // Polyfill deprecated selectors