Hi !
While working on a PR I did some research on layout details and realized that the caution or warning admonitions are rendered the same way in Symfony Doc. See Doctrine (this is warning) and Lock (this is caution) as exemples

I also found #19181 about about a previous work on caution and danger and IMO there is no particular need to introduce more granularity in the admonitions that are available by differentiating caution and warning
So I propose to remove one of the two syntaxes, maybe warning because it's the least used in the documentation

It's probably not a very important topic but looks good one to make documentation writing simpler and more understandable