[CI] Work around to fix v0.x CI

[barry-jin]

Description

It looks like there are some issues in mxnet1.8.0.post0. Freeze mxnet version to 1.7.0 in CI test as work around.

Checklist

Essentials

• PR's title starts with a category (e.g. [BUGFIX], [MODEL], [TUTORIAL], [FEATURE], [DOC], etc)
• Changes are complete (i.e. I finished coding on this PR)
• All changes have test coverage
• Code is well-documented

Changes

• Feature1, tests, (and when applicable, API doc)
• Feature2, tests, (and when applicable, API doc)

Comments

• If this change is a backward incompatible change, why must this change be made.
• Interesting edge cases to note here

cc @dmlc/gluon-nlp-team

[github-actions]

The documentation website for preview: http://gluon-nlp-staging.s3-accelerate.dualstack.amazonaws.com/PR1553/3cf0809fd5854ceee4f530ee4a5755998105a2ca/index.html

[Zha0q1]

Hi @barry-jin any updates on this pr?

[barry-jin]

Hi @barry-jin any updates on this pr?

I'm switching to cudnn8 in docker. Also will try to update website build workflow in #1558 . Currently, the job in workflow will not be marked as failed if the notebook compilation step fails. Check the log here https://github.com/dmlc/gluon-nlp/runs/2366035716?check_suite_focus=true

[barry-jin]

v0.x CI will be fixed in #1558