eth: fix output file permissions in admin_exportChain (ethereum#26912)

* api: Use 0700 file permissions for ExportChain

* change perm to 0644

* Update api.go

---------

Co-authored-by: Felix Lange <fjl@twurst.com>

Author: 2 people

eth/api.go

@@ -161,7 +161,7 @@ func (api *AdminAPI) ExportChain(file string, first *uint64, last *uint64) (bool
 		return false, errors.New("location would overwrite an existing file")
 	}
 	// Make sure we can create the file to export into
-	out, err := os.OpenFile(file, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, os.ModePerm)
+	out, err := os.OpenFile(file, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0644)
 	if err != nil {
 		return false, err
 	}