Revert "contrib/ci.inria.fr/Jenkinsfile-windows: do not delete directory"

This reverts commit c1b0ce62bc8302269f5253939c231a5ad254c14e.

contrib/ci.inria.fr/Jenkinsfile-windows

@@ -83,8 +83,8 @@ pipeline
 									unstash 'script-windows-build'
 									bat './job-1-check-windows.bat'
 									archiveArtifacts artifacts: "*.zip", fingerprint: true, onlyIfSuccessful: true
-									//if (env.KEEP_WORKING_DIRECTORY != 'true')
-									//	deleteDir()
+									if (env.KEEP_WORKING_DIRECTORY != 'true')
+										deleteDir()
 								}
 							}
 						}