[TASK] Remove frameborder attribute if HTML5

HTML5 doesn't know the frameborder attribute which is used
in the Youtube renderer. Therefore only use it if not
HTML5.

Change-Id: I2dc712acb16b79318d18f8199b474e77c4919aae
Resolves: #54527
Reviewed-on: https://review.typo3.org/26560
Reviewed-by: Georg Ringer
Tested-by: Georg Ringer