Ports fix for division documentation that removes "true" rounding mode

[mruberry]

Fixes a design issue identified late in 1.8 development by @gchanan that a "rounding mode" named "true" which performs no rounding is confusing.

[facebook-github-bot]

💊 CI failures summary and remediations

As of commit e356aa3 (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/pytorch-linux-bionic-rocm4.0.1-py3.6

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[codecov]

Codecov Report

Merging #52242 (e356aa3) into release/1.8 (c307a3f) will increase coverage by 0.33%.
The diff coverage is n/a.

@@               Coverage Diff               @@
##           release/1.8   #52242      +/-   ##
===============================================
+ Coverage        80.48%   80.82%   +0.33%     
===============================================
  Files             1948     1948              
  Lines           213183   213183              
===============================================
+ Hits            171588   172296     +708     
+ Misses           41595    40887     -708