fix: increase subsection grades rounding precision

[Agrendalath]

We used two decimal digits to match the experience from the edx-platform. However, openedx/edx-platform#27788 increased the precision to reduce the impact of double rounding.

See the details and testing instructions at openedx/edx-platform#27788.

Private-ref: BB-4210

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.76%. Comparing base (e3ecee1) to head (12fffea).
Report is 5 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1397   +/-   ##
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  Coverage   88.76%   88.76%           
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  Files         305      305           
  Lines        5234     5234           
  Branches     1327     1330    +3     
=======================================
  Hits         4646     4646           
  Misses        572      572           
  Partials       16       16           

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[itsjeyd]

@Agrendalath Thank you for this contribution!

It looks like the older PR that you mentioned in the description (openedx/edx-platform#27788) is tagged for product review. Should we do the same here?

CC @mphilbrick211

[Agrendalath]

@itsjeyd, this is a part of the same product ticket.

[itsjeyd]

@Agrendalath OK great, I'll add the product review label now.