Fix punycode import path in index.js

[alexbevi]

Having the trailing slash on the punycode require causes issues when trying to pre-bundle packages for SSR with Vite that may have tr46 as a transitive dependency.

For example (when using @cloudflare/vite-plugin):

Error: Dynamic require of "punycode/" is not supported
    at /workspace/tanstack/new-test/node_modules/.vite/deps_ssr/chunk-PLDDJCW6.js:11:9
    at node_modules/.pnpm/[email protected]/node_modules/tr46/index.js
    at node_modules/.pnpm/[email protected]/node_modules/whatwg-url/lib/url-state-machine.js

[domenic]

This sounds like a bug in whatever kind of software Vite is; this package is targeted at Node.js.

[baileympearson]

@domenic Yes, Vite probably should handle this and they don't, but is there any reason why we can't just update the import and release a patch? Imports with trailing slashes are not commonly used in the Nodejs ecosystem and Node's resolution algorithm works the same if there isn't a trailing slash.