[Chapel Merge] Fix check for python 3.7 in arkouda testing

Branch: refs/heads/master
Revision: 444a788
Author: ronawho
Log Message:

Merge pull request #16655 from ronawho/fix-arkouda-python37

Fix check for python 3.7 in arkouda testing

Was accidentally using -d to check if a file existed instead of -f

Modified Files:
M util/cron/common-arkouda.bash

Compare: https://github.com/chapel-lang/chapel/compare/f6f49dc9565d...444a788351b8