Update clojure.core-test.take-nth to use doall

[djblue]

So the exception that is being caused by this test is indirectly testing that a Clojure dialect supports IDrop:

• clojure.lang.IDrop - Clojure
• cljs.core/IDrop - ClojureScript
• clojure.lang.IDrop - ClojureCLR

Since jank doesn't implement such an optimization, this test was failing because getting the first element doesn't result in calling pos?. However getting any element after would cause the same exception in jank. You get the exact same behavior in clojure if the collection does not implement IDrop:

% clj
Clojure 1.12.2
user=> (do (seq (take-nth nil (range 10))) :foo) ;; clojure.lang.LongRange implements IDrop
Execution error (NullPointerException) at user/eval1 (REPL:1).
Cannot invoke "Object.getClass()" because "x" is null
user=> (do (seq (take-nth nil (list 0 1))) :foo) ;; clojure.lang.PersistentList does not
:foo
user=> 

I think using doall allows us to ignore this minor implementation detail.

[jeaye]

Thanks!