python: Inline expectation should have space after $

This was a regex-find-replace from `# \$(?! )` (using a negative lookahead) to `# $ `.

python/ql/test/library-tests/frameworks/stdlib-py3/CodeExecution.py

@@ -1,4 +1,4 @@
 import builtins
 
 # exec being part of builtins is Python 3 only
-builtins.exec("print(42)")  # $getCode="print(42)"
+builtins.exec("print(42)")  # $ getCode="print(42)"