Cut lexer recognition of old keywords async, cpp_type
Cut lexer recognition of old keywords async, cpp_type

Summary: [Thrift] Cut lexer recognition of old keywords `async`, `cpp_type`.

Reviewed By: jmswen, stevegury

Differential Revision: D9527748

fbshipit-source-id: fc9188e49359d81b5677eeccbce94fa123633827

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