Remove single-use CodeObject#parent_file_name

Author: st0012

lib/rdoc/code_object.rb

@@ -312,13 +312,6 @@ def parent
     end
   end
 
-  ##
-  # File name of our parent
-
-  def parent_file_name
-    @parent ? @parent.base_name : '(unknown)'
-  end
-
   ##
   # Name of our parent
 

lib/rdoc/code_object/require.rb

@@ -24,7 +24,7 @@ def inspect # :nodoc:
       self.class,
       object_id,
       @name,
-      parent_file_name,
+      @parent ? @parent.base_name : '(unknown)'
     ]
   end
 

test/rdoc/test_rdoc_code_object.rb

@@ -265,11 +265,6 @@ def test_metadata
     assert_equal 'not_rdoc', @co.metadata['markup']
   end
 
-  def test_parent_file_name
-    assert_equal '(unknown)', @co.parent_file_name
-    assert_equal 'xref_data.rb', @c1.parent_file_name
-  end
-
   def test_parent_name
     assert_equal '(unknown)', @co.parent_name
     assert_equal 'xref_data.rb', @c1.parent_name