The patch doesn't apply to the latest development release 8.x.3.x as class 'S...

The patch doesn't apply to the latest development release 8.x.3.x as class 'ServiceAuditFilesUsedNotReferenced' already has a use statement added for 'EntityTypeManagerInterface'. So only changes related to changing 'AccountProxy' to 'AccountProxyInterface' in 'ServiceAuditFilesNotInDatabase' should be fine here.

Marking it as needs work, so that patch can be rerolled to work with 8.x-3.x branch. Website using stable releases can use the patch provided in #3 to get rid of this error.