nazca #221665 Remove iter_wordgrams [validation pending]

Iter wordgrams does not do what it should, and is only used by minhashing.
Minhashing should take an optional tokenizer or call tokenize().

prioritynormal
typebug
done in0.4.1
load0.500
load left0.000
closed by#9cb4aaf1a111 [minhashing] Correctly build k grams in minhashing, closes #221665
patch[minhashing] Correctly build k grams in minhashing, closes #221665 [applied]