indexers: Remove unused PrevScripter interface.

This removes the no longer used PrevScripter interface.

This is part of the overall effort to remove all of the code related to
taking previous script snapshots and feeding them through to the
indexers.

internal/blockchain/indexers/common.go

@@ -35,15 +35,6 @@ var (
 	interruptMsg = "interrupt requested"
 )
 
-// PrevScripter defines an interface that provides access to scripts and their
-// associated version keyed by an outpoint.  It is used within this package as a
-// generic means to provide the scripts referenced by the inputs to transactions
-// within a block that are needed to index it.  The boolean return indicates
-// whether or not the script and version for the provided outpoint was found.
-type PrevScripter interface {
-	PrevScript(*wire.OutPoint) (uint16, []byte, bool)
-}
-
 // ChainQueryer provides a generic interface that is used to provide access to
 // the chain details required by indexes.
 //