Don't know specifically about Google Docs, but since Google Docs is a cloud-based service, it's very, very unlikely that Google would delete documents from the cloud simply because you deleted the app on the phone. That would defeat a key benefit of using the cloud. The cloud assumes that you may be accessing your data from more than one device - deleting the app/erasing the device should not affect your ability to access that data from other devices or the Google web site.
Either by default, or by option, most cloud-based apps also keep copies of the data on your mobile devices and computers, so that you can access the data when you lack an internet connection. In iOS, that locally-stored data would be deleted when you delete the app - that's the standard practice - delete the app, delete the local data. However, the cloud-based data (which is the master), would not be affected.