[CI] Update unittests-gpu

[barry-jin]

Description

Update unittests-gpu.yml to install some required packages.

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

[sxjscience]

Just quickly verifying if github actions work so I will merge this.

[codecov]

Codecov Report

Merging #1313 into master will increase coverage by 0.21%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1313      +/-   ##
==========================================
+ Coverage   84.27%   84.49%   +0.21%     
==========================================
  Files          42       42              
  Lines        6423     6423              
==========================================
+ Hits         5413     5427      +14     
+ Misses       1010      996      -14     

Impacted Files	Coverage Δ
src/gluonnlp/data/loading.py	83.39% <0.00%> (+5.28%)	⬆️

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