`resolve-tag` should ignore local environment

[frenchy64]

AFAIK a tag is resolved from the global environment, not local scope. For example this works fine even though we shadow Class with a local.

(let [Class nil] ((fn [^Class a] (.getName a)) Integer))

(resolve {'Class true} 'Class) ;; emulating Schema's tag inference
;=> nil

(resolve 'Class) ;; what I suspect is more correct
;=> java.lang.Class

Relevant line:

schema/src/clj/schema/macros.clj

Line 121 in 8fcb57f

(let [resolved (delay (resolve env tag))]