[#1745] writecache: Remove `IsErrNotFound`

We specify the error in the doc-comment, and it is the same for all our
components.

Signed-off-by: Evgenii Stratonikov <evgeniy@morphbits.ru>

pkg/local_object_storage/shard/delete.go

@@ -3,7 +3,6 @@ package shard
 import (
 	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/blobstor/common"
 	meta "github.com/nspcc-dev/neofs-node/pkg/local_object_storage/metabase"
-	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/writecache"
 	oid "github.com/nspcc-dev/neofs-sdk-go/object/id"
 	"go.uber.org/zap"
 )
@@ -40,7 +39,7 @@ func (s *Shard) Delete(prm DeletePrm) (DeleteRes, error) {
 	for i := range prm.addr {
 		if s.hasWriteCache() {
 			err := s.writeCache.Delete(prm.addr[i])
-			if err != nil && !writecache.IsErrNotFound(err) {
+			if err != nil && !IsErrNotFound(err) {
 				s.log.Error("can't delete object from write cache", zap.String("error", err.Error()))
 			}
 		}

pkg/local_object_storage/shard/get.go

@@ -100,7 +100,7 @@ func (s *Shard) fetchObjectData(addr oid.Address, skipMeta bool, cb storFetcher,
 			return res, false, err
 		}
 
-		if writecache.IsErrNotFound(err) {
+		if IsErrNotFound(err) {
 			s.log.Debug("object is missing in write-cache")
 		} else {
 			s.log.Error("failed to fetch object from write-cache", zap.Error(err))

pkg/local_object_storage/shard/head.go

@@ -4,7 +4,6 @@ import (
 	"fmt"
 
 	meta "github.com/nspcc-dev/neofs-node/pkg/local_object_storage/metabase"
-	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/writecache"
 	objectSDK "github.com/nspcc-dev/neofs-sdk-go/object"
 	oid "github.com/nspcc-dev/neofs-sdk-go/object/id"
 )
@@ -56,7 +55,7 @@ func (s *Shard) Head(prm HeadPrm) (HeadRes, error) {
 			return HeadRes{
 				obj: header,
 			}, nil
-		} else if !writecache.IsErrNotFound(err) {
+		} else if !IsErrNotFound(err) {
 			// in this case we think that object is presented in write-cache, but corrupted
 			return HeadRes{}, fmt.Errorf("could not read header from write-cache: %w", err)
 		}

pkg/local_object_storage/writecache/errors.go

@@ -1,13 +0,0 @@
-package writecache
-
-import (
-	"errors"
-
-	apistatus "github.com/nspcc-dev/neofs-sdk-go/client/status"
-)
-
-// IsErrNotFound checks if error returned by Cache Get/Head/Delete method
-// corresponds to missing object.
-func IsErrNotFound(err error) bool {
-	return errors.As(err, new(apistatus.ObjectNotFound))
-}