Do not generate GROUP BY clause if options.group is empty

[theosotr]

Fixes: #12315

[codecov]

Codecov Report

Merging #12343 into master will increase coverage by 6.14%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master   #12343      +/-   ##
==========================================
+ Coverage   90.25%   96.40%   +6.14%     
==========================================
  Files          92       95       +3     
  Lines        8973     9116     +143     
==========================================
+ Hits         8099     8788     +689     
+ Misses        874      328     -546     

Impacted Files	Coverage Δ
lib/dialects/abstract/query-generator.js	97.39% <100.00%> (+1.26%)	⬆️
lib/dialects/mssql/query-interface.js	100.00% <0.00%> (ø)
lib/dialects/mssql/index.js	100.00% <0.00%> (ø)
lib/dialects/mssql/connection-manager.js	87.17% <0.00%> (ø)
lib/model.js	96.62% <0.00%> (+0.06%)	⬆️
lib/sequelize.js	95.81% <0.00%> (+0.64%)	⬆️
...dialects/abstract/query-generator/helpers/quote.js	100.00% <0.00%> (+6.66%)	⬆️
lib/dialects/mssql/data-types.js	100.00% <0.00%> (+69.87%)	⬆️
lib/dialects/mssql/async-queue.js	100.00% <0.00%> (+76.47%)	⬆️
... and 2 more

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[sushantdhiman]

This needs tests, please add new file group.test.js here, assert that group: [] do not generate any group by statement

[theosotr]

done