Tweak Dependabot to not group QuickJS + ignore wasmtime

[jeffcharles]

Description of the change

Tweaks Dependabot configuration to do two things:

• Stop grouping rquickjs updates in with the non-breaking updates. We have to be very careful with these so they should be inspected separately.
• Ignore Wasmtime updates. Wizer is generally going to pin Wasmtime to a particular version.

Why am I making this change?

Trying to get on top of the Dependabots opened this month and one of them is for rquickjs which I want to evaluate separately.

Checklist

• I've updated the relevant CHANGELOG files if necessary. Changes to javy-cli and javy-plugin do not require updating CHANGELOG files.
• I've updated the relevant crate versions if necessary. Versioning policy for library crates
• I've updated documentation including crate documentation if necessary.

[saulecabrera]

Good call.