Fixes
https://github.com/tailwindlabs/tailwindcss-intellisense/issues/1328
The alpha and beta releases used `_` in theme keys to represent a `.`.
This meant we used `--leading-1_5` instead of `--leading-1\.5` to add
utilities like `leading-1.5`. We prefer the use of the escaped dot now
but still want to make sure suggestions for the legacy key format still
works as expected when surrounded by numbers.
This is the same as #16433 but for `@utility` since we apparently missed
this when emitting suggestions for it
8bf06ab770