update all Windows jobs to windows-2019 (#1714)

Summary:
Pull Request resolved: https://github.com/facebook/folly/pull/1714

windows-2016 will be removed in March, and now that we've updated
Boost, we can upgrade to windows-2019.

Reviewed By: genevievehelsel

Differential Revision: D34119171

fbshipit-source-id: caad432bebf6b8282844bf79f82b1fbc34f2df9e

.github/workflows/getdeps_windows.yml

@@ -12,7 +12,7 @@ on:
 
 jobs:
   build:
-    runs-on: windows-2016
+    runs-on: windows-2019
     steps:
     - uses: actions/checkout@v2
     - name: Export boost environment

build/fbcode_builder/getdeps.py

@@ -906,12 +906,8 @@ class GenerateGitHubActionsCmd(ProjectCmdBase):
             artifacts = "linux"
             runs_on = f"ubuntu-{args.ubuntu_version}"
         elif build_opts.is_windows():
-            # We're targeting the windows-2016 image because it has
-            # Visual Studio 2017 installed, and at the time of writing,
-            # the version of boost in the manifests (1.69) is not
-            # buildable with Visual Studio 2019
             artifacts = "windows"
-            runs_on = "windows-2016"
+            runs_on = "windows-2019"
             # The windows runners are python 3 by default; python2.exe
             # is available if needed.
             py3 = "python"