Hi! Since you've used export, the environment variable has been set for the whole session, so one option would be to just set export PRODIGY_CONFIG_OVERRIDES="{}" to reset it to an empty dict.
I'm not sure if this happened while copy-pasting or if this was the actual output, but based on the error message, it looks like you somehow ended up with typographic quotes, e.g. “ instead of "? So that's the first thing I would check. If you want to be extra sure, you can also run echo $PRODIGY_CONFIG_OVERRIDES and then copy-paste the output to Python's json.loads as a string. If that succeeds, it should be valid.