feat: govern GetBucketVersioning with the regular access checks

S3 explicitly documents this action as owner-only ("To retrieve the versioning state of a bucket, you must be the bucket owner." — https://docs.aws.amazon.com/AmazonS3/latest/API/API_GetBucketVersioning.html), and the handler enforced that with an extra auth.IsAdminOrOwner check on top of VerifyAccess. Real S3 behaves differently: verified against AWS that a bucket policy explicitly denying s3:GetBucketVersioning denies the bucket owner itself, and that an Allow grants the action to a principal that doesn't own the bucket. It goes through ordinary bucket policy/ACL evaluation like any other bucket subresource read, which is what the write side, PutBucketVersioning, already did here. Removes the extra check along with auth.IsAdminOrOwner, which had no other call site.

auth/access-control.go

@@ -618,26 +618,6 @@ func verifyIdentityOnlyAccess(ctx fiber.Ctx, pe PolicyEvaluator, acc Account, ac
 	return s3err.GetImplicitDenyAccessErr(principal, string(action), resourceArn)
 }
 
-func IsAdminOrOwner(acct Account, isRoot bool, acl ACL) error {
-	// Owner check
-	if acct.Access == acl.Owner {
-		return nil
-	}
-
-	// Root user has access over almost everything
-	if isRoot {
-		return nil
-	}
-
-	// Admin user case
-	if acct.Role == RoleAdmin {
-		return nil
-	}
-
-	// Return access denied in all other cases
-	return s3err.GetAPIError(s3err.ErrAccessDenied)
-}
-
 type PublicACLAllowedActions map[Action]struct{}
 
 var publicACLAllowedActions PublicACLAllowedActions = PublicACLAllowedActions{