Copyedit parallel test harness crash message

tool/lib/test/unit.rb

@@ -473,8 +473,8 @@ module Test
         real_file = worker.real_file and warn "running file: #{real_file}"
         @need_quit = true
         warn ""
-        warn "Some worker was crashed. It seems ruby interpreter's bug"
-        warn "or, a bug of test/unit/parallel.rb. try again without -j"
+        warn "Some test worker crashed. It might an interpreter bug or"
+        warn "a bug in test/unit/parallel.rb. Try again without the -j"
         warn "option."
         warn ""
         if File.exist?('core')