dev-cmd/audit: enforce uses_from_macos only if core tap

Library/Homebrew/dev-cmd/audit.rb

@@ -388,7 +388,8 @@ module Homebrew
             "use the canonical name '#{dep.to_formula.full_name}'."
           end
 
-          if @new_formula &&
+          if @core_tap &&
+             @new_formula &&
              dep_f.keg_only? &&
              dep_f.keg_only_reason.provided_by_macos? &&
              dep_f.keg_only_reason.applicable? &&

Library/Homebrew/test/dev-cmd/audit_spec.rb

@@ -343,7 +343,7 @@ module Homebrew
           subject { fa }
 
           let(:fa) do
-            formula_auditor "foo", <<~RUBY, new_formula: true
+            formula_auditor "foo", <<~RUBY, new_formula: true, core_tap: true
               class Foo < Formula
                 url "https://brew.sh/foo-1.0.tgz"
                 homepage "https://brew.sh"