Passing BUILD_TAGS variable to build Gitaly is no more effective

Overview

Passing BUILD_TAGS variable to build Gitaly is no more effective while !1284 (merged), !960 (merged), !987 (merged), !968 (merged), and !742 (merged) modified the code introduced in !596 (merged) since gitaly is now using GO_BUILD_TAGS instead.

https://gitlab.com/gitlab-org/gitlab-development-kit/-/blob/b1f69281605831c0a1ceeebb6cd727dd0eb0c964/Makefile#L436