contrib/ci.inria.fr/Jenkinsfile-windows: partly revert last commit

contrib/ci.inria.fr/Jenkinsfile-windows

@@ -82,8 +82,8 @@ pipeline
 									unstash 'script-windows-check'
 									unstash 'script-windows-build'
 									bat './job-1-check-windows.bat'
-//									if (env.KEEP_WORKING_DIRECTORY != 'true')
-//										deleteDir()
+									if (env.KEEP_WORKING_DIRECTORY != 'true')
+										deleteDir()
 								}
 							}
 						}