the_platinum_searcher 1.6.4 (new formula)

`the_platinum_searcher` (`pt`) is code search tool, similar to `ack`
and `the_silver_searcher` (`ag`), but is written in Go to enable
easier multi-platform support.
the_platinum_searcher: add 1.6.4 bottle.

Closes #30527.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>