Fix incorrect _disconnect_raise docstring

[mohsinhaider]

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)?
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Description of change

Updates docstring for _disconnect_raise to correctly reflect code

[codecov-commenter]

Codecov Report

Base: 92.23% // Head: 92.21% // Decreases project coverage by -0.01% ⚠️

Coverage data is based on head (cc92f06) compared to base (ed38e77).
Patch has no changes to coverable lines.

Additional details and impacted files

@@ Coverage Diff @@ ## master #2534 +/- ## ========================================== - Coverage 92.23% 92.21% -0.02%  ========================================== Files 113 113 Lines 29388 29388 ========================================== - Hits 27106 27101 -5  - Misses 2282 2287 +5 

Impacted Files	Coverage Δ
redis/asyncio/client.py	92.51% <ø> (ø)
tests/test_cluster.py	96.79% <0.00%> (-0.23%)	⬇️
tests/test_asyncio/test_cluster.py	97.48% <0.00%> (-0.13%)	⬇️
tests/test_asyncio/test_pubsub.py	99.53% <0.00%> (+0.15%)	⬆️

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