fix autonaming issue in groupings sets for special symbols

[jangorecki]

closes #3653

[codecov]

Codecov Report

Merging #3738 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #3738      +/-   ##
==========================================
+ Coverage   98.81%   98.81%   +<.01%     
==========================================
  Files          69       69              
  Lines       13285    13292       +7     
==========================================
+ Hits        13127    13134       +7     
  Misses        158      158

Impacted Files	Coverage Δ
R/groupingsets.R	96.87% <100%> (+0.24%)	⬆️

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[codecov]

Codecov Report

Merging #3738 into master will decrease coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #3738      +/-   ##
==========================================
- Coverage   99.41%   99.41%   -0.01%     
==========================================
  Files          71       71              
  Lines       13216    13208       -8     
==========================================
- Hits        13139    13131       -8     
  Misses         77       77

Impacted Files	Coverage Δ
R/groupingsets.R	100% <100%> (ø)	⬆️

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[jangorecki]

Code simplified, no need for workarounds because by=.() already works. Related #3270.