Issue 21469:  Minor code modernization (convert and/or expression to an if/else expression).

Suggested by: Tal Einat
diff --git a/Lib/urllib/robotparser.py b/Lib/urllib/robotparser.py
index 1d7b751..4fbb0cb 100644
--- a/Lib/urllib/robotparser.py
+++ b/Lib/urllib/robotparser.py
@@ -172,7 +172,7 @@
         return self.path == "*" or filename.startswith(self.path)
 
     def __str__(self):
-        return (self.allowance and "Allow" or "Disallow") + ": " + self.path
+        return ("Allow" if self.allowance else "Disallow") + ": " + self.path
 
 
 class Entry: