fbcode_builder: getdeps: Update OpenNSA to 6.5.19
fbcode_builder: getdeps: Update OpenNSA to 6.5.19

Summary: 6.5.19 is now available, switch OSS to pick that instead of old 6.5.17.

Reviewed By: rsunkad

Differential Revision: D22199286

fbshipit-source-id: 231346df8d2f918d2226cfe17b01bde12c18a5a7

facebookincubator/mvfst,facebookincubator/mvfst,facebookincubator/mvfst,facebookincubator/mvfst,facebookincubator/mvfst