fix display of the 'host not found' message

The conversion of characters like _space_ in qstrs is a bit
ad-hoc. Because "_not_" stands for the logical negation character ¬
the recently added message was displayed incorrectly:
```
>>> socket.getaddrinfo('does.not.exist', 0)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
gaierror: (-2, 'Name or service_space¬space_known')
```
I had noticed this, but evidently failed to include the fix in
the problem in #7269.

Author: jepler

py/makeqstrdefs.py

@@ -65,6 +65,7 @@
 # These are just vexing!
 del name2codepoint["and"]
 del name2codepoint["or"]
+del name2codepoint["not"]
 
 
 def preprocess():