test: add v3_relativeSplatPath future flag in Remix test utils (#223)

* test: silence react-router future warnings in vitest

* fix: use v3_relativeSplatPath instead of invalid v7_ future flags

The FutureConfig type in @remix-run/react only has v3_ prefix flags:
- v3_fetcherPersist
- v3_relativeSplatPath
- v3_lazyRouteDiscovery
- v3_singleFetch

Remove invalid v7_startTransition (no v3 equivalent for this flag)
and correct v7_relativeSplatPath → v3_relativeSplatPath.

Fixes TypeScript type check failure in CI.

* test: remove redundant React Router warning suppression

Amp-Thread-ID: https://ampcode.com/threads/T-019c7d08-04f2-743c-9527-500a06f0ea9f
Co-authored-by: Amp <amp@ampcode.com>

---------

Co-authored-by: Wheeljack <wheeljack@zavi.family>
Co-authored-by: Amp <amp@ampcode.com>

Author: 3 people

test/test-utils.tsx

@@ -22,7 +22,14 @@ export function createRemixStubWrapper(
       Component: () => ui,
     },
   ])
-  return <RemixStub initialEntries={initialEntries} />
+  return (
+    <RemixStub
+      initialEntries={initialEntries}
+      future={{
+        v3_relativeSplatPath: true,
+      }}
+    />
+  )
 }
 
 /**