Export to .idml, open that and save as a new .indd. That should clear the plugin info.
If Peter's solution does not help, here's another way, because the missing plugin might just be incorrectly registered or not at all:
1. Find the location of your Indesign preferences file, copy it to a safe place, delete the original.
2. Start Indesign - it will re-register all plugins. Close Indesign again.
3. Write back the saved prefs file to the original location.
I have created a plugin to strip missing plugin info from the documents, you can try it out at the following location
Currently its available only for CC2017 MAC, let me know your thoughts on the product. You will have to Save As only once, the first time you save the document after ignoring the missing plugins using my inexutils plugin and then you are all set to go.
Suggestions for improvements are always welcome