main_ERC.cwl Docker image version 1 not available

[dhardestylewis]

Change mintproject/aquifer:v1 to mintproject/aquifer:latest in main_ERC.cwl to correspond with publicly available / existing Docker image version in DockerHub:
https://hub.docker.com/r/mintproject/aquifer/tags?page=1&ordering=last_updated

Here's this minor change on my GitHub fork:
dhardestylewis@266f54b#diff-b57f45b6a88e5d9c4d6a54a26e039725e0158d20a6e663a77b248e690450149b

[dhardestylewis]

Which allows this issue to be avoided:

(pyclass) taccstaff@TACCs-MacBook-Pro-2 aquifer % cwltool main_ERC.cwl values.yml
INFO /Users/taccstaff/miniconda3/envs/pyclass/bin/cwltool 3.0.20201203173111   
INFO Resolved 'main_ERC.cwl' to 'file:///Users/taccstaff/SWAT/aquifer/main_ERC.cwl'
ERROR Workflow error, try again with --debug for more information:
Docker is not available for this tool, try --no-container to disable Docker, or install a user space Docker replacement like uDocker with --user-space-docker-cmd.: Docker image mintproject/aquifer:v1 not found