graph mode: add docs to pre-calibration passes

[vkuzo]

Stack from ghstack:

• qat graph mode: add combine_conv_bn pass #39828 [wip] qat graph mode: add combine_conv_bn pass
• eager qat: refactor conv-bn to make conv with scaled weights a func #39837 eager qat: refactor conv-bn to make conv with scaled weights a func
• qat graph mode: make _forward of per channel observers scriptable #39840 qat graph mode: make per channel observers scriptable
• qat graph mode: initial scaffolding for prepare_qat_script #39796 qat graph mode: initial scaffolding for prepare_qat_script
• graph mode: add quantization type enum #39795 graph mode: add quantization type enum
• graph mode qat: make fake_quantize scriptable #39750 graph mode qat: make fake_quantize scriptable
• graph mode: more docs for insert observers pass #39739 graph mode: more docs for insert observers pass
• graph mode: add docs to pre-calibration passes #39683 graph mode: add docs to pre-calibration passes

Summary:

Adding a couple of docstrings to _jit_pass_dedup_module_uses and
_jit_pass_insert_observers.

Test Plan:

CI, no logic change

Reviewers:

Subscribers:

Tasks:

Tags:

Differential Revision: D21975880

[jerryzh168]

LG Thanks!

[dr-ci]

💊 CI failures summary and remediations

As of commit e17393c (more details on the Dr. CI page):

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• 1/1 failures possibly* introduced in this PR
  • 1/1 non-CircleCI failure(s)

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ci.pytorch.org: 1 failed

• Failed: pr/caffe2-py3.6-devtoolset7-rocmrpm-centos7-test

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[facebook-github-bot]

This pull request has been merged in f8561ac.