Skip clean step in Windows test runs

Author: murgatroid99

run-tests.bat

@@ -55,7 +55,6 @@ for %%v in (10 12) do (
 
   node -e "process.exit(process.version.startsWith('v%%v') ? 0 : -1)" || goto :error
 
-  call .\node_modules\.bin\gulp cleanAll || SET FAILED=1
   call .\node_modules\.bin\gulp setup || SET FAILED=1
   call .\node_modules\.bin\gulp test || SET FAILED=1
   cmd.exe /c "SET GRPC_DNS_RESOLVER=ares& call .\node_modules\.bin\gulp nativeTestOnly" || SET FAILED=1