typecheck: Fix #17633 by checking tycon in equation LHS
Issue #17633 (closed) point out that we fail to verify that the type constructor in the LHS of a closed type family equantion matches the name of the family. Fix this.
Issue #17633 (closed) point out that we fail to verify that the type constructor in the LHS of a closed type family equantion matches the name of the family. Fix this.