remove duplicate definition of dynamic::print_as_pseudo_json
remove duplicate definition of dynamic::print_as_pseudo_json

Summary:
`folly/test/DynamicTest.cpp` contained a duplicate definition of
`dynamic::print_as_pseudo_json()`.  This caused link errors due if this test
was linked against `json.cpp`.

Part of the problem here is that the `//folly:dynamic` library is somewhat of
a lie: the `dynamic::print_as_pseudo_json()` method is provided by the
`//folly:json` library rather than by `//folly:dynamic`.  This violates
assumptions made by autodeps.  Ultimately the right thing to do might be to
combine `//folly:json` and `//folly:dynamic` into a single rule.

Reviewed By: yangchi

Differential Revision: D8020841

fbshipit-source-id: e563611309c122680a5fc69c3f0da1ad5d4337b0

facebook/folly,facebook/folly,facebook/folly,facebook/folly,facebook/folly