Drop tests of $id and $anchor against meta-schema pattern

[notEthan]

Per discussion at #716
These tests rely on the meta-schemas' pattern keywords for $id and $anchor, rather than anything particular to $id/$anchor keywords.

Relevant historical links:

• Add tests for invalid anchors. #567
• [299, 300] Add tests for invalid use of, and valid use of empty, fragments in "$id" #341

[jdesrosiers]

Thanks!