Used "fixed-version:" prefix in a test

Author: owen-mc

go/ql/test/library-tests/semmle/go/dataflow/ExternalTaintFlow/steps.ext.yml

@@ -3,7 +3,7 @@ extensions:
       pack: codeql/go-all
       extensible: summaryModel
     data:
-      - ["github.com/nonexistent/test", "T", False, "StepArgRes", "", "", "Argument[0]", "ReturnValue", "taint", "manual"]
+      - ["fixed-version:github.com/nonexistent/test", "T", False, "StepArgRes", "", "", "Argument[0]", "ReturnValue", "taint", "manual"]
       - ["github.com/nonexistent/test", "T", False, "StepArgRes1", "", "", "Argument[0]", "ReturnValue[1]", "taint", "manual"]
       - ["github.com/nonexistent/test", "T", False, "StepArgArg", "", "", "Argument[0]", "Argument[1]", "taint", "df-generated"]
       - ["github.com/nonexistent/test", "T", False, "StepArgArgIgnored", "", "", "Argument[0]", "Argument[1]", "taint", "df-generated"]