bpo-44145: Release the GIL around HMAC_Update. (GH-26157) It was always meant to be released for parallelization. This now matches the other similar code in the module. Thanks michaelforney for noticing! (cherry picked from commit c10392e7ddb3eafbd11e9ffe335c07648426715f) Co-authored-by: Gregory P. Smith <greg@krypto.org>