Rank checking should only run against exploit modules

Author: sinn3r

tools/msftidy.rb

@@ -74,6 +74,8 @@ def test_old_rubies(f_rel)
 	end
 
 	def check_ranking
+		return if @source !~ / \< Msf::Exploit/
+
 		available_ranks = [
 			'ManualRanking',
 			'LowRanking',