docs: fix broken and placeholder links (#4097)

* docs: fix broken and placeholder links

Fix the two links called out in #4094 plus one more found while scanning
all docs: the NOTE:addlinktoLOC placeholder in async.mdx now points at
_aggregate_action_queues in robot_client.py; the dead
#mapping-videoencoderconfig--ffmpeg-options anchor in
video_encoding_parameters.mdx now points at get_codec_options in
video.py; and the stale ./cameras#setup-cameras fragment in il_robots.mdx
is dropped to link the cameras guide page.

Closes #4094.

* docs: apply prettier formatting to the video-encoding parameter table

Re-align the Markdown table columns with prettier (v3.6.2, --prose-wrap=preserve)
so the pre-commit 'Format Markdown with Prettier' hook passes. Whitespace only.

docs/source/async.mdx

@@ -65,7 +65,7 @@ In summary, you need to specify instructions for:
 Importantly,
 
 - `actions_per_chunk` and `chunk_size_threshold` are key parameters to tune for your setup.
-- `aggregate_fn_name` is the function to aggregate actions on overlapping portions. You can either add a new one to a registry of functions, or add your own in `robot_client.py` (see [here](NOTE:addlinktoLOC))
+- `aggregate_fn_name` is the function to aggregate actions on overlapping portions. You can either add a new one to a registry of functions, or add your own in `robot_client.py` (see [here](https://github.com/huggingface/lerobot/blob/main/src/lerobot/async_inference/robot_client.py#L224))
 - `debug_visualize_queue_size` is a useful tool to tune the `CLIENT` parameters.
 
 ## Done! You should see your robot moving around by now 😉