Python: Do not alter codeql-workspaces.yml

And remove the qlpack referred to therein.
Instead we rename and duplicate the extesion file
that this qlpack pointed to.
These two extension files are kept in sync by `identical-files.json`.

config/identical-files.json

@@ -571,5 +571,9 @@
   "EncryptionKeySizes Python/Java": [
     "python/ql/lib/semmle/python/security/internal/EncryptionKeySizes.qll",
     "java/ql/lib/semmle/code/java/security/internal/EncryptionKeySizes.qll"
+  ],
+  "Python model summaries test extension": [
+    "python/ql/test/experimental/dataflow/model-summaries/InlineTaintTest.ext.yml",
+    "python/ql/test/experimental/dataflow/model-summaries/NormalDataflowTest.ext.yml"
   ]
-}
+}