Return correct error on invalid grantee type

[smallhive]

Closes #908.

[codecov]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (f76190c) 33.68% compared to head (205f942) 33.68%.
Report is 1 commits behind head on master.

Files	Patch %	Lines
api/handler/acl.go	33.33%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #926   +/-   ##
=======================================
  Coverage   33.68%   33.68%           
=======================================
  Files          64       64           
  Lines       10834    10834           
=======================================
  Hits         3649     3649           
  Misses       6777     6777           
  Partials      408      408           

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[roman-khimov]

I don't see this documented anywhere.

[smallhive]

I don't see this documented anywhere.

neofs-s3-gw/docs/aws_s3_compat.md

Line 54 in 90de859

* Only `CanonicalUser` (with hex encoded public key) and `All Users Group` are supported in [ACL](https://docs.aws.amazon.com/AmazonS3/latest/userguide/acl-overview.html).