Remove "aria-required" attribute when "required" attribute is already used

[audrasjb]

Quote from Andrea in #39045 :

There was a time when both were needed. Today, it's safe to use just required. Instead, aria-required is for custom, non-native, controls. Also, just stumbled upon a good feedback from Adrian Roselli: ​https://stackoverflow.com/a/37975985

I found both aria-required and required attributes used in the following file:

• wp-admin/includes/media.php L. 1672, 1674, 1849, 2756, 2763 and note also that it should use required instead of aria-required at L. 2772.

Related: #39045

[Shital Patel]

I added patch for media.php

[afercia]

@Shital Patel thanks for the patch. A good best practice for patches is to try to not introduce unrelated changes, see onclick and readonly in 43415.patch​ better to not change them. Also, required is a boolean attribute that means it doesn't need to have a specified value required="required" and the correct syntax is just required.

[SergeyBiryukov]

In 42759:

Media: Remove unnecessary aria-required attribute from legacy (pre-3.5.0) media functions, added in [7888].

At the time, having both required and aria-required meant a wider range of support for browsers and assistive technology. Today, it's safe to use just required.

Props shital-patel, afercia, audrasjb.
Fixes #43415.

[audrasjb]

Reopening for 4.9.9 consideration as seen during accessibility team bug-scrub meeting.