Change scope of ndarray custom validators

As noted in a comment:

Lines 7 to 9 in 5e3983e

    
           # The validators in this module should really only be applied 
        
           # to ndarray-* tags, but that will have to be a 3.0 change. 
        
           tags = ["**"]

Prior to new-style extension custom validators the ndarray related validated applied to all tags. Scoping these to ndarray makes sense. This missed the 3.0 release and could be included in 4.0

Doh, duplicate of #1693

	# The validators in this module should really only be applied
	# to ndarray-* tags, but that will have to be a 3.0 change.
	tags = ["**"]