backend/cache: use backend types not restic types (#21860)

internal/backend/cache/cache.go

@@ -12,7 +12,6 @@ import (
 	"github.com/pkg/errors"
 	"github.com/restic/restic/internal/backend"
 	"github.com/restic/restic/internal/debug"
-	"github.com/restic/restic/internal/restic"
 )
 
 // Cache manages a local cache.
@@ -43,10 +42,10 @@ func readVersion(dir string) (v uint, err error) {
 
 const cacheVersion = 1
 
-var cacheLayoutPaths = map[restic.FileType]string{
-	restic.PackFile:     "data",
-	restic.SnapshotFile: "snapshots",
-	restic.IndexFile:    "index",
+var cacheLayoutPaths = map[backend.FileType]string{
+	backend.PackFile:     "data",
+	backend.SnapshotFile: "snapshots",
+	backend.IndexFile:    "index",
 }
 
 const cachedirTagSignature = "Signature: 8a477f597d28d172789f06886806bc55\n"