deps: upgrade pytest-cov to 6.2.1 and remove unused coveralls dependency

- Upgrade pytest-cov from 5.0.0 to 6.2.1 for Python 3.13 and coverage 7.x compatibility
- Remove coveralls==3.3.1 dependency as it's unused and conflicts with coverage 7.x
- Eliminates Python 3.13 deprecation warning: "co_lnotab is deprecated, use co_lines instead"
- Project uses local coverage reports only, no external coverage service integration

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: AndreyNikiforov

pyproject.toml

@@ -62,9 +62,8 @@ test = [
     "mock==5.2.0",
     "freezegun==1.5.2",
     "vcrpy==7.0.0",
-    "pytest-cov==5.0.0",
+    "pytest-cov==6.2.1",
     "ruff==0.11.13",
-    "coveralls==3.3.1",
     "pytest-timeout==2.4.0",
     "pytest-xdist==3.7.0",
     "mypy==1.16.0",