fix: missing case in setxattr error handling (#26176)

ENOTSUP case is present in vim, but doesn't appear to have included here.

src/nvim/os/fs.c

@@ -795,6 +795,7 @@ void os_copy_xattr(const char *from_file, const char *to_file)
         case E2BIG:
           errmsg = e_xattr_e2big;
           goto error_exit;
+        case ENOTSUP:
         case EACCES:
         case EPERM:
           break;