docs(runtime): add JSDoc to and rename callNodeRefs (#4251)

This is a really small change that was overlooked when a bunch of JSDoc
was added to this file in #3931. The `callNodeRefs` function is renamed
to `nullifyVNodeRefs` and a JSDoc comment is added as well.

src/runtime/vdom/vdom-render.ts

@@ -249,7 +249,7 @@ const removeVnodes = (vnodes: d.VNode[], startIdx: number, endIdx: number, vnode
   for (; startIdx <= endIdx; ++startIdx) {
     if ((vnode = vnodes[startIdx])) {
       elm = vnode.$elm$;
-      callNodeRefs(vnode);
+      nullifyVNodeRefs(vnode);
 
       if (BUILD.slotRelocation) {
         // we're removing this element
@@ -778,10 +778,17 @@ const isNodeLocatedInSlot = (nodeToRelocate: d.RenderNode, slotNameAttr: string)
   return slotNameAttr === '';
 };
 
-export const callNodeRefs = (vNode: d.VNode) => {
+/**
+ * 'Nullify' any VDom `ref` callbacks on a VDom node or its children by
+ * calling them with `null`. This signals that the DOM element corresponding to
+ * the VDom node has been removed from the DOM.
+ *
+ * @param vNode a virtual DOM node
+ */
+export const nullifyVNodeRefs = (vNode: d.VNode) => {
   if (BUILD.vdomRef) {
     vNode.$attrs$ && vNode.$attrs$.ref && vNode.$attrs$.ref(null);
-    vNode.$children$ && vNode.$children$.map(callNodeRefs);
+    vNode.$children$ && vNode.$children$.map(nullifyVNodeRefs);
   }
 };