bump gha instance to 16 core / 64 gigs of ram

Differential Revision: D41821039

fbshipit-source-id: aad96d314a9e653bb321373488e0703e60fcc1aa

Author: Kyle Sugrue

.github/workflows/getdeps_linux.yml

@@ -6,7 +6,7 @@ on: [push, pull_request]
 
 jobs:
   build:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-20.04-16core
     steps:
     - uses: actions/checkout@v2
     - name: Fetch boost