Enables "requireReturnType" for valid-jsdoc lint rule (#3374)

.eslintrc

@@ -31,7 +31,7 @@
       "requireReturnDescription": false,
       "requireReturn": false,
       "requireParamDescription": false,
-      "requireReturnType": false
+      "requireReturnType": true
       }],
     }
     // To flag presence of console.log without breaking linting:

lib/network/modules/LayoutEngine.js

@@ -238,7 +238,7 @@ class HierarchicalStatus {
    *
    * @param {vis.Node} node1
    * @param {vis.Node} node2
-   * @return true if the two nodes have a same ancestor node, false otherwise
+   * @return {boolean} true if the two nodes have a same ancestor node, false otherwise
    */
   hasSameParent(node1, node2) {
     let parents1 = this.parentReference[node1.id];
@@ -263,7 +263,7 @@ class HierarchicalStatus {
    *
    * @param {vis.Node} node1
    * @param {vis.Node} node2
-   * @return true if this is so, false otherwise
+   * @return {Boolean} true if this is so, false otherwise
    */
   inSameSubNetwork(node1, node2) {
     return (this.trees[node1.id] === this.trees[node2.id]);