src/index.js: Do not null elements array

If we set `this.elements.length = 0`; aka truncating the array
then we cannot move this TonicComponent in the DOM as that
fires disconnected followed by connected callback.

Any component that renders `this.html`${this.elements}`` cannot
be safely moved around.

index.js

@@ -349,8 +349,6 @@ class Tonic extends window.HTMLElement {
 
   disconnectedCallback () {
     Tonic._maybePromise(this.disconnected && this.disconnected())
-    this.elements.length = 0
-    this.nodes.length = 0
     delete Tonic._data[this._id]
     delete Tonic._children[this._id]
   }