Use system trust store by default

[bigcat88]

After internal discussion with @kyteinsky when we tested this nextcloud/app_api#448 - it was found out that the test-deploy ExApp from AppAPI "Test Deploy" button action fails in such setups, since the Python library "httpx" ignores system certificates by default.

reference: encode/httpx#302

Temporary workaround, until "httpx" will change it's behavior.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.68%. Comparing base (78a6f76) to head (a4d859d).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #328   +/-   ##
=======================================
  Coverage   94.68%   94.68%           
=======================================
  Files          46       46           
  Lines        5365     5367    +2     
=======================================
+ Hits         5080     5082    +2     
  Misses        285      285           

Files with missing lines	Coverage Δ
nc_py_api/_version.py	100.00% <100.00%> (ø)
nc_py_api/options.py	100.00% <100.00%> (ø)