Diagnostic: remove need for headers on 10.14

Library/Homebrew/extend/os/mac/diagnostic.rb

@@ -20,7 +20,6 @@ module Homebrew
           check_xcode_minimum_version
           check_clt_minimum_version
           check_if_xcode_needs_clt_installed
-          check_if_clt_needs_headers_installed
         ].freeze
       end
 
@@ -138,17 +137,6 @@ module Homebrew
         EOS
       end
 
-      def check_if_clt_needs_headers_installed
-        return unless MacOS::CLT.separate_header_package?
-        return if MacOS::CLT.headers_installed?
-
-        <<~EOS
-          The Command Line Tools header package must be installed on #{MacOS.version.pretty_name}.
-          The installer is located at:
-            #{MacOS::CLT::HEADER_PKG_PATH.sub(":macos_version", MacOS.version)}
-        EOS
-      end
-
       def check_for_other_package_managers
         ponk = MacOS.macports_or_fink
         return if ponk.empty?

Library/Homebrew/test/os/mac/diagnostic_spec.rb

@@ -32,19 +32,6 @@ describe Homebrew::Diagnostic::Checks do
       .to match("Xcode alone is not sufficient on El Capitan")
   end
 
-  specify "#check_if_clt_needs_headers_installed" do
-    allow(MacOS).to receive(:version).and_return(OS::Mac::Version.new("10.14"))
-    allow(MacOS::CLT).to receive(:installed?).and_return(true)
-    allow(MacOS::CLT).to receive(:headers_installed?).and_return(false)
-
-    expect(subject.check_if_clt_needs_headers_installed)
-      .to match("The Command Line Tools header package must be installed on Mojave.")
-
-    allow(MacOS).to receive(:version).and_return(OS::Mac::Version.new("10.13"))
-    expect(subject.check_if_clt_needs_headers_installed)
-      .to be_nil
-  end
-
   specify "#check_homebrew_prefix" do
     # the integration tests are run in a special prefix
     expect(subject.check_homebrew_prefix)