[docs] dump_ast_matchers strips internal::(Bindable)?Matcher from Result_type

Summary: Remove `internal::Matcher` and `internal::BindableMatcher` from Result Type when dumping AST Matchers

Reviewers: joerg, gribozavr2, aaron.ballman

Reviewed By: aaron.ballman

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D75046