Fix CLI help text for render command

[mtfum]

• Problem: sharp render --help shows the same description as predict (“Predict Gaussians from input images.”), which is misleading.
• Fix: Update the render command docstring so the CLI help correctly states that it renders videos from predicted Gaussians with a camera trajectory (CUDA only).
• Behavior: No functional change; help text only.
• Validation: sharp render --help now displays the corrected description.

❯ sharp render --help
Usage: sharp render [OPTIONS]

Render videos from predicted Gaussians with a camera trajectory (CUDA only).

Options:
-i, --input-path PATH        Path to the ply or a list of plys.  [required]
-o, --output-path DIRECTORY  Path to save the rendered videos.  [required]
-v, --verbose                Activate debug logs.
--help                       Show this message and exit.