Correct $TMP creation

The pub directory is not included in the sparse checkout, and the nektos/act tool for testing locally doesn’t do an actual sparse checkout (it does `docker cp` instead) so I didn’t catch this issue locally.

.github/workflows/publish-data.sh

@@ -1,7 +1,7 @@
 # See publish-data.yml
 
 TMP=pub/tmp
-mkdir $TMP
+mkdir -p $TMP
 
 COPY_YEAR=$(date -u +%Y)
 PUB_DATE=$(date -u +%Y-%m-%d)