[API] Remove get_bert_model from the public API list

[eric-haibin-lin]

Description

As title. Everything should go through nlp.model.get_model. @szha @leezu

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

[codecov]

Codecov Report

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[codecov]

Codecov Report

❗ No coverage uploaded for pull request head (get_bert_model_api@7a04b89). Click here to learn what that means.
The diff coverage is n/a.

[mli]

Job PR-767/1 is complete.
Docs are uploaded to http://gluon-nlp-staging.s3-accelerate.dualstack.amazonaws.com/PR-767/1/index.html

[eric-haibin-lin]

@rich-junwang FYI we are replacing get_bert_model API with the get_model API

[mli]

Job PR-767/2 is complete.
Docs are uploaded to http://gluon-nlp-staging.s3-accelerate.dualstack.amazonaws.com/PR-767/2/index.html

[mli]

Job PR-767/3 is complete.
Docs are uploaded to http://gluon-nlp-staging.s3-accelerate.dualstack.amazonaws.com/PR-767/3/index.html