Get rid of python2 support

[volodymyrZotov]

Users ask to get rid of python2 support as it is not possible for them to use this Connect client in new projects.

The changes are done in PR:

• Remove six package.
• Update all dependencies to the latest versions.

The package is functionally tested. No issues were found after applying the changes.

Resolves #59

[codecov-commenter]

Codecov Report

Base: 76.29% // Head: 76.11% // Decreases project coverage by -0.17% ⚠️

Coverage data is based on head (3a3ddb6) compared to base (5e70b02).
Patch coverage: 14.28% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #61      +/-   ##
==========================================
- Coverage   76.29%   76.11%   -0.18%     
==========================================
  Files          21       21              
  Lines        1599     1587      -12     
==========================================
- Hits         1220     1208      -12     
  Misses        379      379              

Impacted Files	Coverage Δ
src/onepasswordconnectsdk/models/error.py	40.00% <0.00%> (-1.18%)	⬇️
src/onepasswordconnectsdk/models/field.py	82.60% <0.00%> (-0.15%)	⬇️
src/onepasswordconnectsdk/models/field_section.py	53.65% <0.00%> (-1.11%)	⬇️
src/onepasswordconnectsdk/models/file.py	40.90% <0.00%> (-0.89%)	⬇️
src/onepasswordconnectsdk/models/item.py	86.62% <0.00%> (-0.09%)	⬇️
src/onepasswordconnectsdk/models/item_details.py	40.00% <0.00%> (-1.18%)	⬇️
src/onepasswordconnectsdk/models/item_urls.py	40.81% <0.00%> (-1.19%)	⬇️
src/onepasswordconnectsdk/models/item_vault.py	52.50% <0.00%> (-1.16%)	⬇️
src/onepasswordconnectsdk/models/section.py	61.22% <0.00%> (-0.78%)	⬇️
src/onepasswordconnectsdk/models/summary_item.py	78.57% <0.00%> (-0.16%)	⬇️
... and 2 more

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[edif2008]

This looks good to me. A couple of questions before approving this PR:

• Have you checked whether the current versions of the dependencies support only Python 3.7 or higher? (just to double-check)
• Are there any dependencies that we no longer need? It may be a good cleanup opportunity with this PR.
• Any idea why the test coverage dropped? I know it's very small (by 0.17%), but would like to know the reason for it.

Also, one small notice. Since you've removed the six dependency in a couple of files, now we have two new lines between the imports and the code itself. I believe having only one is enough, so you can remove the extra newline as well.

[volodymyrZotov]

@edif2008 Thank you for reviewing!

1. It works with higher versions. The latest I tried was v3.10.5.
2. Nothing to clean up right now. We need all of them.
3. Good question. Don't have an exact answer, unfortunately. The detailed test report says nothing also.

And regarding the code formatting.
Pycharm suggest to use new 2 lines between imports section and the rest of the code PEP 8: E302 expected 2 blank lines, found 1. I'd stick with 2, as it was before the changes also.