Include the help header in the gem

The built gem didn't include the help header fixture. Just inline
the text.

Author: joshcooper

.rubocop.yml

@@ -47,6 +47,7 @@ Naming/MethodName:
   Exclude:
     - 'spec/mocks/win32ole.rb'
     - 'spec/mocks/ffi.rb'
+    - 'spec/facter/util/windows/network_utils_spec.rb'
 
 Naming/PredicateName:
   Exclude:

lib/facter/fixtures/facter_help_header

@@ -167,20 +167,26 @@ def list_cache_groups
     end
 
     desc '--help, -h', 'Help for all arguments'
-    def help(*args)
+    def help(*_args)
       help_string = +''
-      help_string << help_header(args)
+      help_string << help_header
       help_string << add_class_options_to_help
       help_string << add_commands_to_help
 
       puts help_string
     end
 
     no_commands do
-      def help_header(_args)
-        path = File.join(File.dirname(__FILE__), '../../')
+      def help_header
+        <<~HELP
+          Usage
+          =====
 
-        Facter::Util::FileHelper.safe_read("#{path}fixtures/facter_help_header")
+          facter [options] [query] [query] [...]
+
+          Options
+          =======
+        HELP
       end
 
       def add_class_options_to_help