streams: Prevent cursor jump to the end of editing stream-descr.

This prevents the cursor to jump at the end of the content-editable
area when the user types in the middle.

Fixes #4202.

static/js/click_handlers.js

@@ -476,7 +476,6 @@ $(function () {
             // wrong.
             if (this.hasChildNodes()) {
                 this.innerText = this.innerText;
-                place_caret_at_end(this);
             }
         });