docs: remove future work for highlight (#16)

Since it is implemented at
MaikoTan/cactbot-highlight#406 and released in
version 0.6.0.

~~Please call me Sonic Maiko~~

Preview:

![image](https://github.com/OverlayPlugin/cactbot/assets/19927330/8ff773c3-2d5f-4fea-887d-8dffc6da8fa5)

docs/TimelineGuide.md

@@ -1213,7 +1213,6 @@ There's plenty of feature work and fixes for timelines if you are interested in
 
 ### Smaller Fixes/Changes
 
-* update [Cactbot Highlight](https://marketplace.visualstudio.com/items?itemName=MaikoTan.cactbot-highlight) to include new `Ability { params }` style syncs
 * make it so you can pass multiple mob names to `-it`
 * `test_timeline.ts` could know which file to use without `-t` (it could use `ZoneChange` lines to look up the correct timeline)
 * `make_timeline.ts` has issues with empty names: <https://github.com/quisquous/cactbot/issues/5943>