Repeat support

Well, maybe I just misunderstand the relationship between nil and empty list/vector, I just delete this entry, and delete test cases that constrained on nil and repeat list/vector in [nil-empty-with-repeat](https://github.com/clojure/core.typed/commit/35158d4340b1afda3b4073ae6efd7d6b1b08ea7e#diff-97b4dfca878dc0ed8badb483dc921e72R3290) and it passed all the test cases, so this entry wasn't used in any other places.

The reason I did this in the first place is repeat list/vector should accept empty list/vector, which implemented in [here](https://github.com/clojure/core.typed/commit/e929d55ab5ab3218f62a8711e7d58f0fd7ff80cc#diff-c119fbca96f4acba6c6d7f967d5bee67R514), also because I thought nil and empty list/vector is the same thing, I added this.

Well, this *is* an error. Sorry, should I submit a patch or you just fix it?