Update bug issue template

[kubukoz]

The suggestion to try nightlies would've saved me about 10 minutes because I would've seen @som-snytt already fixed #22901...

[skip ci]

[som-snytt]

I see he opened that PR on April 1, so just from his PR comment, I can't tell whether it's an actual fix or an elaborate hoax.

However, this is a useful suggestion for the bug template, which still mentions scalac instead of scala-cli. Just today, I had to look up dep syntax, which is mill style, because the link to scastie only shows sbt config. It's especially helpful to have the "directives" all ready to go for scala-cli. Oh, in fact, the template could be pre-populated with directive syntax for using scala, using dep, and using options.

My other suggestion is probably too many words, it would just clutter up the template:

If you're not sure what version you're using, maybe you shouldn't be submitting a bug report for the compiler.

If possible, check if your issue appears in the nightly version of the compiler!

If that's not possible, maybe you shouldn't be submitting a bug report for the compiler.

[som-snytt]

Maybe the AI assistant read your suggestion and decided to compile with scala-cli while using scala 3.nightly.

There is a directive to avoid running the CI, if I could remember it.

[som-snytt]

I added some words from the perspective of someone who might try out the buggy code, but feel free to drop it if it clouds the issue, so to speak.