feat(sveltekit): Only inject fetch proxy script for SvelteKit < 2.16.0 (#15126)

With v9 onwards, we'll only inject the fetch proxy script into SvelteKit
versions where we actually need it. This is all kit versions below
2.16.0. I'll update docs in a follow-up PR.

fixes #15007

Author: Lms24

dev-packages/e2e-tests/test-applications/sveltekit-2-twp/.gitignore renamed to dev-packages/e2e-tests/test-applications/sveltekit-2.5.0-twp/.gitignore

@@ -1,5 +1,5 @@
 {
-  "name": "sveltekit-2-svelte-5",
+  "name": "sveltekit-2.5.0-twp",
   "version": "0.0.1",
   "private": true,
   "scripts": {
@@ -22,7 +22,7 @@
     "@sentry-internal/test-utils": "link:../../../test-utils",
     "@sentry/core": "latest || *",
     "@sveltejs/adapter-auto": "^3.0.0",
-    "@sveltejs/kit": "^2.0.0",
+    "@sveltejs/kit": "2.5.0",
     "@sveltejs/vite-plugin-svelte": "^3.0.0",
     "svelte": "^5.0.0-next.115",
     "svelte-check": "^3.6.0",