Fix reference to non-existent tanstackstart-router (#14393)

## DESCRIBE YOUR PR

The docs reference @sentry/tanstackstart-router which does not exist.
The function is exported by @sentry/tanstackstart-react though

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Author: johnf

docs/platforms/javascript/guides/tanstackstart-react/index.mdx

@@ -138,7 +138,7 @@ Wrap TanStack Start's `createRootRoute` function using `wrapCreateRootRouteWithS
 ```tsx {filename:src/routes/__root.tsx} {3,6}
 import type { ReactNode } from "react";
 import { createRootRoute } from "@tanstack/react-router";
-import { wrapCreateRootRouteWithSentry } from "@sentry/tanstackstart-router";
+import { wrapCreateRootRouteWithSentry } from "@sentry/tanstackstart-react";
 
 // (Wrap `createRootRoute`, not its return value!)
 export const Route = wrapCreateRootRouteWithSentry(createRootRoute)({