Simplify bound_t function in Ty_normalizer
Simplify bound_t function in Ty_normalizer

Summary:
`symbol_from_reason` just calls `Reason.def_aloc_of_reason` and then passes the result into `symbol_from_loc`. `symbol_from_loc` computes `sym_provenance` and `sym_anonymous` but just passes through the name and location that is provided to it.

We can just call `Reason.dec_aloc_of_reason` directly and save some trouble.

Reviewed By: panagosg7

Differential Revision: D26415394

fbshipit-source-id: bc592f875d8c3bb582dd6a1f36b1b5f27383c32e

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