docs: correct claims.email in github guide (#422)

There is no email_primary in claims, and the selfservice strategy is currently using claims.email.

docs/versioned_docs/version-v0.3/guides/sign-in-with-github-google-facebook-linkedin.mdx

@@ -70,7 +70,7 @@ local claims = {
       //
       // Therefore we only return the email if it (a) exists and (b) is marked verified
       // by GitHub.
-      [if "email_primary" in claims && claims.email_verified then "email" else null]: claims.email_primary,
+      [if "email" in claims && claims.email_verified then "email" else null]: claims.email,
     },
   },
 }