Update java/ql/lib/ext/retrofit2.model.yml

Author: atorralba

java/ql/lib/ext/retrofit2.model.yml

@@ -8,4 +8,4 @@ extensions:
       pack: codeql/java-all
       extensible: summaryModel
     data:
-      - ["retrofit2", "Retrofit$Builder", False, "baseUrl", "(String)", "", "Argument[undefined]", "ReturnValue", "taint", "ai-manual"]
+      - ["retrofit2", "Retrofit$Builder", False, "baseUrl", "(String)", "", "Argument[this]", "ReturnValue", "taint", "ai-manual"]