Update README.md and CI to use spack-stack-1.7.0

[climbfuji]

Description

All in the title.

CI tests passed for commit d2f574d with the temporary change from commit b5f4dd6 - this particular commit was reverted after https://github.com/JCSDA-internal/fv3-jedi/pull/1181 got merged.

Issue(s) addressed

n/a

Dependencies

• waiting on https://github.com/JCSDA-internal/fv3-jedi/pull/1181
• waiting on https://github.com/JCSDA-internal/fv3-jedi/pull/1183

Impact

Expected impact on downstream repositories:

Checklist

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have run the unit tests before creating the PR

[srherbener]

Changes look good. I looked at the rendering of the README.md at the feature branch, and noticed a typo that is not part of these changes. Thought you might want to fix that. It is on line 58 where the text has beig and I'm guessing that intention is being.

[climbfuji]

Changes look good. I looked at the rendering of the README.md at the feature branch, and noticed a typo that is not part of these changes. Thought you might want to fix that. It is on line 58 where the text has beig and I'm guessing that intention is being.

Thanks Steve, fixed