There is no method to remove a specific Pure1 authentication in the vSphere Plugin today. The public key that pairs with the private key used to generate it can be removed from Pure1.
Login to pure1.purestorage.com and click on API registration. Find the application deauthenticate is desired for.
Navigate to the far right and click on the trashcan icon:
Confirm the deletion. This will de-authenticate any integration using the correlated private key from authenticating (or any JWT that has been derived from it).