Use predicate methods instead of inspecting the tags array

Library/Homebrew/cmd/audit.rb

@@ -148,9 +148,9 @@ class FormulaAuditor
       dep.options.reject do |opt|
         next true if dep_f.build.has_option?(opt.name)
         dep_f.requirements.detect do |r|
-          if r.tags.include? :recommended
+          if r.recommended?
             opt.name == "with-#{r.name}"
-          elsif r.tags.include? :optional
+          elsif r.optional?
             opt.name == "without-#{r.name}"
           end
         end

Library/Homebrew/cxxstdlib.rb

@@ -38,7 +38,7 @@ class CxxStdlib
         # Software is unlikely to link against anything from its
         # buildtime deps, so it doesn't matter at all if they link
         # against different C++ stdlibs
-        next if dep.tags.include? :build
+        next if dep.build?
 
         dep_stdlib = Tab.for_formula(dep.to_formula).cxxstdlib
         if !compatible_with? dep_stdlib

Library/Homebrew/requirements/python_dependency.rb

@@ -14,7 +14,7 @@ class PythonDependency < Requirement
   end
 
   def pour_bottle?
-    tags.include?(:build) || system_python?
+    build? || system_python?
   end
 
   def modify_build_environment