[easy] inline logic of poly_type_of_tparams
[easy] inline logic of poly_type_of_tparams

Summary: avoids creating an id that never gets used

Reviewed By: samwgoldman

Differential Revision: D23247160

fbshipit-source-id: 38ba0089b230d217affd36febc1f26889ed8bde7

nmote/flow,nmote/flow,nmote/flow,nmote/flow,nmote/flow,nmote/flow,nmote/flow