Change QHeaderView active section style

[5yutan5]

Whether the QTableView section header is active or not is represented by a border. However, this border breaks rounded border of QTableView.

Change QHeaderView active header style and fix round border of QTableView.

[codecov[bot]]

Codecov Report

Merging #218 (dbda413) into main (0e17642) will not change coverage. The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #218   +/-   ##
=======================================
  Coverage   98.39%   98.39%           
=======================================
  Files          39       39           
  Lines        1432     1432           
=======================================
  Hits         1409     1409           
  Misses         23       23           

Impacted Files	Coverage Δ
qdarktheme/_resources/_template_stylesheet.py	100.00% <100.00%> (ø)

:mega: We’re building smart automated test selection to slash your CI/CD build times. Learn more