Remove unnecessary assignment for string encoding

Author: sds

lib/overcommit/hook_context/pre_commit.rb

@@ -19,7 +19,7 @@ def amendment?
       # containing unicode characters, we replace the offending characters,
       # since the pattern we're looking for will consist of ASCII characters
       unless cmd.valid_encoding?
-        cmd = cmd.encode('UTF-16be', invalid: :replace, replace: '?').encode('UTF-8')
+        cmd.encode!('UTF-16be', invalid: :replace, replace: '?').encode!('UTF-8')
       end
 
       return @amendment if