fix: remove --system flag from uv pip install in CI

The --system flag prevents uv from using virtual environments,
which causes failures on macOS with Homebrew's externally-managed Python.

Removing the flag allows uv to handle virtual environments automatically,
fixing the CI error while maintaining the same functionality.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: abrichr

.github/workflows/screenshots.yml

@@ -50,12 +50,12 @@ jobs:
       - name: Install openadapt-capture
         working-directory: openadapt-capture
         run: |
-          uv pip install -e . --system
+          uv pip install -e .
 
       - name: Install openadapt-viewer with screenshots extra
         working-directory: openadapt-viewer
         run: |
-          uv pip install -e ".[screenshots]" --system
+          uv pip install -e ".[screenshots]"
 
       - name: Install Playwright browsers
         working-directory: openadapt-viewer