Remove use of six.reraise (#28887)

Implementation of this for Python 3:
https://github.com/web-platform-tests/wpt/blob/aa9b753e75bb0c7de5a05277c91cef3a7a7348e4/tools/third_party/six/six.py#L697-L706

Simplifying that step by step leads to the new code.

Part of #28776.

webdriver/tests/support/sync.py

@@ -2,8 +2,6 @@
 import sys
 import time
 
-import six
-
 from webdriver import error
 
 
@@ -140,6 +138,6 @@ def until(self, condition):
             message = "Timed out after {} seconds".format(elapsed)
             if self.exc_msg is not None:
                 message = "{} with message: {}".format(message, self.exc_msg)
-            six.reraise(self.exc_cls, self.exc_cls(message=message), tb)
+            raise self.exc_cls(message=message).with_traceback(tb)
         else:
             return rv