Only inject fetch proxy script if SvelteKit<2.16.0 is used

[Lms24]

Description

We should find a way to only inject the fetch proxy script if the SDK is used in a SvelteKit version older than 2.16.0. With this version, the proxy script no longer is necessary.

[Lms24]

I re-purposed this issue because it turned out that we can't remove the script, as it's still necessary in Kit versions between 2.0.0 and 2.16.0.