Fix round-trip of IPv6 addresses when converting to a string

[bdraco]

What do these changes do?

The brackets were missing when the URL was convert to a string

fixes #1157
regressed in #1033

Are there changes in behavior for the user?

no

[webknjaz]

I wonder if this is where we could finally stick a hypothesis-based property test..

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.48%. Comparing base (7d013d2) to head (ed85d2b).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1158      +/-   ##
==========================================
+ Coverage   95.46%   95.48%   +0.01%     
==========================================
  Files          30       30              
  Lines        4807     4825      +18     
  Branches      428      429       +1     
==========================================
+ Hits         4589     4607      +18     
  Misses        192      192              
  Partials       26       26              

Flag	Coverage Δ
CI-GHA	95.44% <100.00%> (+0.01%)	⬆️
MyPy	41.56% <66.66%> (+0.16%)	⬆️
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OS-Windows	99.50% <100.00%> (+0.05%)	⬆️
OS-macOS	99.12% <100.00%> (+0.05%)	⬆️
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Py-pypy7.3.16	99.25% <100.00%> (+0.05%)	⬆️
Py-pypy7.3.17	99.28% <100.00%> (+0.05%)	⬆️
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VM-ubuntu-latest	99.40% <100.00%> (+0.05%)	⬆️
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pytest	99.40% <100.00%> (+0.05%)	⬆️

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[bdraco]

I wonder if this is where we could finally stick a hypothesis-based property test..

It would be really nice to get #860 going. The open PRs list is shrinking enough that is coming to the top soon.