Issue #16714: use 'raise' exceptions, don't 'throw'.

Patch by Serhiy Storchaka.
diff --git a/Lib/runpy.py b/Lib/runpy.py
index f635c4b..c4d7cc2 100644
--- a/Lib/runpy.py
+++ b/Lib/runpy.py
@@ -200,7 +200,7 @@
                 pass
         else:
             # The following check looks a bit odd. The trick is that
-            # NullImporter throws ImportError if the supplied path is a
+            # NullImporter raises ImportError if the supplied path is a
             # *valid* directory entry (and hence able to be handled
             # by the standard import machinery)
             try: