Some users could be setting their `signIn` and `error` pages option to
`/` to disable the automatically generated pages, as suggested in [1].

This commit reverts the behaviour for matching `signIn` and `error`
pages in `handleMiddleware` to pre-v4.10.3.

```
const signInPage = "/"
const errorPage = "/"
const publicPaths = [signInPage, errorPage, "/_next", "/favicon.ico"]

// pathname = "/" will return true
publicPaths.some((p) => pathname.startsWith(p))
```

Fixes: aedabc8 ("fix: avoid redirect on always public paths")
Reference [1]: #2330 (reply in thread)
Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>

Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>