chore(python): add --port option to the instruction

Should be in 2fc1114 commit.

Relate to #16

src/generator/PyGenerator.js

@@ -5,7 +5,7 @@ module.exports = class PyGenerator {
   pip install -r requirements.txt
 to install its dependencies and
   export DB_NAME=db DB_USER=user DB_PASSWORD=secret
-  uvicorn app:app
+  uvicorn app:app --port 3000
 afteward to run`
     }