Update custom sign in getProvider example

According to the function declaration for [getProviders()](https://github.com/nextauthjs/next-auth/blob/v4/packages/next-auth/src/react/index.tsx#L187) it doesn't accept any parameters. Therefore have removed passing of an argument in the doc example.

Using the documentation as is will result in multiple type errors as [referenced in an issue I've posted about](nextauthjs#6704)

docs/docs/configuration/pages.md

@@ -107,10 +107,10 @@ export async function getServerSideProps(context: GetServerSidePropsContext) {
     return { redirect: { destination: "/" } };
   }
 
-  const providers = await getProviders(context);
+  const providers = await getProviders();
 
   return {
-    props: { providers: Object.values(providers) ?? [] },
+    props: { providers: providers ?? [] },
   }
 }
 ```