.datepicker("show") does not work on class selector

**The version(s) of the jQuery project that are affected.

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JQuery 1.12.4 and JQueryUI 1.12.1

**The browser (or browsers) that you are able to reproduce the bug in, including version numbers.

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chrome 89.0.4389.90, Firefox 85.0.1

**The operating system (or operating systems) you experienced the bug on.**\\\\

Windows 10 pro 10.0.18363 Build 18363

**Step-by-step instructions on how to reproduce the issue, including any required system configuration changes.

A description of what you expect to happen, and what actually happens.**\\\\

Open one of the 2 links below, when clicking on the input element I expect the datepicker to open, but in the broken version an error is thrown.

**A link to a reduced, working demo/test case that will never move (jsFiddle is good for this).**\\\\

Broken (with class): https://jsbin.com/yumurejixe/edit?html,console,output\\\\

Working (with id): https://jsbin.com/cujiziqeto/edit?html,console,output