update preview version tag (#3016)

Signed-off-by: Wenqi Li <[email protected]>

Author: wyli

.github/workflows/weekly-preview.yml

@@ -33,7 +33,7 @@ jobs:
         export YEAR_WEEK=$(date +'%y%U')
         echo "Year week for tag is ${YEAR_WEEK}"
         if ! [[ $YEAR_WEEK =~ ^[0-9]{4}$ ]] ; then echo "Wrong 'year week' format.  Should be 4 digits."; exit 1 ; fi
-        git tag "0.7.dev${YEAR_WEEK}"
+        git tag "0.8.dev${YEAR_WEEK}"
         git log -1
         git tag --list
         python setup.py sdist bdist_wheel