[Doc] Remove duplicates in global settings

[isdanni]

Issue

No Related issue;

Description

Super minor typo in docs/global_settings.rst.
Noticed there's an extra . while I was updating the CN version and it kept bugging me so thought I'd remove it lol.

The last line in the following photo:

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[codecov]

Codecov Report

Merging #1328 into master will increase coverage by 0.08%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1328      +/-   ##
==========================================
+ Coverage   66.40%   66.48%   +0.08%     
==========================================
  Files          37       37              
  Lines        5155     5156       +1     
  Branches      939      939              
==========================================
+ Hits         3423     3428       +5     
+ Misses       1568     1564       -4     
  Partials      164      164              

Impacted Files	Coverage Δ
python/taichi/lang/expr.py	89.82% <100.00%> (+0.06%)	⬆️
python/taichi/lang/util.py	64.07% <0.00%> (+2.39%)	⬆️

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[archibate]

Thank for pointing out!