Add dialect to ft aggregate

[DvirDukhan]

Pull Request check-list

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• Does $ tox pass with this change (including linting)?
• Do the CI tests pass with this change (enable it first in your forked repo and wait for the github action build to finish)?
• Is the new or changed code fully tested?
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Description of change

Added dialect option to aggregate command

[codecov-commenter]

Codecov Report

Base: 92.23% // Head: 92.22% // Decreases project coverage by -0.01% ⚠️

Coverage data is based on head (0c782d4) compared to base (f10c81a).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2537      +/-   ##
==========================================
- Coverage   92.23%   92.22%   -0.02%     
==========================================
  Files         113      113              
  Lines       29380    29388       +8     
==========================================
+ Hits        27098    27102       +4     
- Misses       2282     2286       +4     

Impacted Files	Coverage Δ
redis/commands/search/aggregation.py	79.72% <100.00%> (+0.85%)	⬆️
tests/test_asyncio/test_search.py	98.63% <100.00%> (+<0.01%)	⬆️
tests/test_search.py	99.16% <100.00%> (+<0.01%)	⬆️
tests/test_cluster.py	96.79% <0.00%> (-0.34%)	⬇️
tests/conftest.py	85.71% <0.00%> (+0.77%)	⬆️

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