[lint] Correctly suppress BUILDIFIERLINT

Summary:
`lint-ignore` and `lint-ignore-every` bluntly silence any issue,
whereas buildifier suppression directives allow for precise narrow
per-issue suppression. So replace them.

Test Plan: `arc lint` comes back clean

Reviewed By: dtolnay

Differential Revision: D47348679

fbshipit-source-id: a56c0ee97ac1a9066094b7dfff3bff6a203b5d94

antlir/bzl/image/feature/install.bzl

@@ -199,7 +199,7 @@ def feature_install(
         user = "root",
         group = "root",
         separate_debug_symbols = True,
-        # @lint-ignore BUILDIFIERLINT
+        # buildifier: disable=unused-variable
         wrap_as_buck_runnable = False):
     """
 `feature.install("//path/fs:data", "dir/bar")` installs file or directory