Relax constraint on `getEntity`
Relax constraint on `getEntity`

This was probably a copy & paste error in #620. There's no need to require a `PersistStoreWrite` when only doing a get operation.
yesodweb/persistent,naushadh/persistent,plow-technologies/persistent,psibi/persistent,bitemyapp/persistent,gbwey/persistent,gbwey/persistent,gbwey/persistent,creichert/persistent,paul-rouse/persistent,erikd/persistent