[rb] Force UTF-8 encoding on logger

This should solve warnings from #6937

Author: p0deje

rb/lib/selenium/webdriver/common/logger.rb

@@ -185,7 +185,7 @@ def create_logger(name, level:)
         logger.progname = name
         logger.level = level
         logger.formatter = proc do |severity, time, progname, msg|
-          "#{time.strftime('%F %T')} #{severity} #{progname} #{msg}\n"
+          "#{time.strftime('%F %T')} #{severity} #{progname} #{msg}\n".force_encoding('UTF-8')
         end
 
         logger