Fix async_timeout deprecation warning.

[yuxincs]

Proposed Changes

A very simple fix for the deprecation warning from async_timeout when testing home assistant's adguard integration:

tests/components/adguard/test_config_flow.py: 32 warnings
 /homeassistant/lib/python3.9/site-packages/adguardhome/adguardhome.py:135: DeprecationWarning: with timeout() is deprecated, use async with timeout() instead
    with async_timeout.timeout(self.request_timeout):

Related Issues

[codecov]

Codecov Report

Merging #471 (ff20470) into main (2014fe2) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##              main      #471   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            9         9           
  Lines          287       287           
  Branches        27        27           
=========================================
  Hits           287       287           

Impacted Files	Coverage Δ
src/adguardhome/adguardhome.py	100.00% <100.00%> (ø)

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[frenck]

Thanks, @yxwangcs 👍