Set dropdown to fixed height of `250px` and make it scrollable

app/assets/stylesheets/pages/pipelines.scss

@@ -218,6 +218,11 @@
       }
     }
 
+    .dropdown-menu {
+      max-height: 250px;
+      overflow-y: auto;
+    }
+
     .dropdown-toggle,
     .dropdown-menu {
       color: $gl-text-color-secondary;

app/assets/stylesheets/pages/projects.scss

@@ -271,6 +271,13 @@
   }
 }
 
+.project-repo-buttons {
+  .project-action-button .dropdown-menu {
+    max-height: 250px;
+    overflow-y: auto;
+  }
+}
+
 .split-one {
   display: inline-table;
   margin-right: 12px;