Revert "fix path parsing bug on windows (prysmaticlabs#14931)"

This reverts commit e39f44b.

Author: hunterfd99988

beacon-chain/db/filesystem/iteration.go

@@ -3,6 +3,7 @@ package filesystem
 import (
 	"fmt"
 	"io"
+	"path"
 	"path/filepath"
 	"strconv"
 	"strings"
@@ -192,7 +193,7 @@ func rootFromPath(p string) ([32]byte, error) {
 }
 
 func idxFromPath(p string) (uint64, error) {
-	p = filepath.Base(p)
+	p = path.Base(p)
 
 	if !isSszFile(p) {
 		return 0, errors.Wrap(errNotBlobSSZ, "does not have .ssz extension")