[WEBSITE] update button style

[szha]

Description

update button style for tutorials and model zoo

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)

Changes

• update button style

[mli]

Job PR-869/1 is complete.
Docs are uploaded to http://gluon-nlp-staging.s3-accelerate.dualstack.amazonaws.com/PR-869/1/index.html

[codecov]

Codecov Report

Merging #869 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #869   +/-   ##
=======================================
  Coverage   90.22%   90.22%           
=======================================
  Files          66       66           
  Lines        6340     6340           
=======================================
  Hits         5720     5720           
  Misses        620      620

[codecov]

Codecov Report

Merging #869 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #869   +/-   ##
=======================================
  Coverage   90.22%   90.22%           
=======================================
  Files          66       66           
  Lines        6340     6340           
=======================================
  Hits         5720     5720           
  Misses        620      620

[codecov]

Codecov Report

Merging #869 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #869   +/-   ##
=======================================
  Coverage   90.22%   90.22%           
=======================================
  Files          66       66           
  Lines        6340     6340           
=======================================
  Hits         5720     5720           
  Misses        620      620

[codecov]

Codecov Report

Merging #869 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #869   +/-   ##
=======================================
  Coverage   90.22%   90.22%           
=======================================
  Files          66       66           
  Lines        6340     6340           
=======================================
  Hits         5720     5720           
  Misses        620      620

[mli]

Job PR-869/2 is complete.
Docs are uploaded to http://gluon-nlp-staging.s3-accelerate.dualstack.amazonaws.com/PR-869/2/index.html

[mli]

Job PR-869/3 is complete.
Docs are uploaded to http://gluon-nlp-staging.s3-accelerate.dualstack.amazonaws.com/PR-869/3/index.html

[mli]

Job PR-869/4 is complete.
Docs are uploaded to http://gluon-nlp-staging.s3-accelerate.dualstack.amazonaws.com/PR-869/4/index.html