Python: Fix grammar

Co-authored-by: Taus <tausbn@github.com>

Author: RasmusWL

python/ql/test/experimental/query-tests/Security-new-dataflow/CWE-078-py2/command_injection.py

@@ -11,7 +11,7 @@
 def python2_specific():
     """
     These tests are mostly included to check for extra paths that can be generated if
-    we can track flow into the implementation of stdlib function, and then to an other sink.
+    we can track flow into the implementation of a stdlib function, and then to another sink.
     See comment in query for more details.
     """