style: Apply black format

[janickm]

This pull request mainly focuses on improving code readability and formatting across several files, primarily by reformatting long lines and function arguments for better clarity. No functional or behavioral changes are introduced.

Formatting and readability improvements:

• Reformatted long type annotations and default assignments for render_mode and colormap in the GsplatRenderTabState class to be more concise and readable in both examples/gsplat_viewer.py and examples/gsplat_viewer_2dgs.py. [1] [2]
• Reformatted assignments in the _after_render method to use single-line expressions with parentheses in both examples/gsplat_viewer.py and examples/gsplat_viewer_2dgs.py. [1] [2]
• Reformatted multi-line assignments and function calls for better readability in gsplat/compression/png_compression.py, gsplat/cuda/_lidar.py, and tests/test_2dgs.py. [1] [2] [3]
• Converted abstract method definitions to single-line format in gsplat/cuda/_torch_cameras.py.
• Added a blank line for consistency in gsplat/cuda/_torch_lidars.py.
• Added a trailing comma for argument consistency in tests/test_cameras.py.

[janickm]

[looks like I used a wrong black version locally - closing]