chore(ci): experiment with splitting Windows further

Windows is the slowest test run, a problem made worse
by the time consuming build process that runs before it.

Perhaps a short term workaround until we have time to
optimise the build step is to increase the number of shards.

.circleci/config.yml

@@ -581,6 +581,7 @@ workflows:
           test_snyk_command: binary-releases\\snyk-win.exe
           install_deps_extension: windows-full
           dont_skip_tests: 0
+          shards: 4
           pre_test_cmds: Import-Module $env:ChocolateyInstall\helpers\chocolateyProfile.psm1; RefreshEnv
 
       - sign: