fix docs for password protected socket access

[hofrob]

Pull Request check-list

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Description of change

In #2374 @dvora-h answered my confusion regarding connecting to a password protected redis server using a unix socket. This change adapts the documentation of the from_url methods to reflect this.

The password needs to be added as a GET parameter. The user still needs to be handed over as part of the URL auth part.

[codecov-commenter]

Codecov Report

Base: 92.04% // Head: 92.03% // Decreases project coverage by -0.00% ⚠️

Coverage data is based on head (2854974) compared to base (16270e4).
Patch has no changes to coverable lines.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2378      +/-   ##
==========================================
- Coverage   92.04%   92.03%   -0.01%     
==========================================
  Files         110      110              
  Lines       28705    28705              
==========================================
- Hits        26421    26420       -1     
- Misses       2284     2285       +1     

Impacted Files	Coverage Δ
redis/asyncio/client.py	92.22% <ø> (ø)
redis/asyncio/connection.py	86.38% <ø> (ø)
redis/client.py	89.06% <ø> (ø)
redis/cluster.py	89.85% <ø> (ø)
redis/connection.py	86.30% <ø> (ø)
tests/test_asyncio/test_search.py	98.26% <0.00%> (-0.35%)	⬇️
tests/test_asyncio/test_pubsub.py	99.37% <0.00%> (-0.16%)	⬇️
tests/test_cluster.py	96.96% <0.00%> (ø)
tests/test_asyncio/test_cluster.py	97.42% <0.00%> (+0.13%)	⬆️

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[chayim]

Thanks @hofrob for helping improve the documentation! This is great ❤️