Remove unused modified_lines helper from HookContext::Base

This was deprecated in 89b7d7b. It is now safe to remove.

Author: sds

lib/overcommit/hook_context/base.rb

@@ -59,14 +59,6 @@ def modified_files
       []
     end
 
-    # Returns a set of lines that have been modified for a file.
-    #
-    # By default, this returns an empty set. Subclasses should implement if
-    # there is a concept of files changing for the type of hook being run.
-    def modified_lines(_file)
-      Set.new
-    end
-
     # Returns an array of lines passed to the hook via STDIN.
     def input_lines
       @input_lines ||= @input.read.split("\n")

lib/overcommit/hook_context/pre_commit.rb

@@ -99,13 +99,6 @@ def modified_files
       @modified_files
     end
 
-    # @deprecated
-    # TODO: Remove this once we've moved all existing hooks to stop using this
-    # endpoint
-    def modified_lines(file)
-      modified_lines_in_file(file)
-    end
-
     # Returns the set of line numbers corresponding to the lines that were
     # changed in a specified file.
     def modified_lines_in_file(file)