FIX-#6779: pass only one indexer into Series.__getitem__

[anmyachev]

What do these changes do?

• first commit message and PR title follow format outlined here

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• passes flake8 modin/ asv_bench/benchmarks scripts/doc_checker.py
• passes black --check modin/ asv_bench/benchmarks scripts/doc_checker.py
• signed commit with git commit -s
• Resolves pandas.errors.IndexingError: Too many indexers: you're trying to pass 2 indexers to the <class 'modin.pandas.series.Series'> having only 1 dimensions. #6779
• tests added and passing
• module layout described at docs/development/architecture.rst is up-to-date