Remove $wgAllowMicroDataAttributes and $wgAllowRdfaAttributes

Remove $wgAllowMicroDataAttributes and $wgAllowRdfaAttributes

$wgAllowMicroDataAttributes and $wgAllowRdfaAttributes have been
introduced in MediaWiki 1.16 and required at this moment $wgHTML5
to be true. This last setting has been removed in MediaWiki 1.22.

To simplify the code maintenance and the configuration complexity,
those settings are removed and the features are always available.

RDFa users must now explicitly set $wgHtml5Version to a RDFa
version. Currently the correct values are:

  - HTML+RDFa 1.0
  - XHTML+RDFa 1.0

Bug: T130040
Change-Id: I17a7bff2cad170e381eabf0aec4e26e4fd0cddc3