Remove unused variable

Commit 82329ca1 introduced this var
but never ended up using it. Remove to avoid compiler warnings on
unused var.

src/backend/utils/misc/fstream/gfile.c

@@ -1025,8 +1025,6 @@ gfile_close(gfile_t*fd)
 		}
 		else
 		{
-			int i;
-
 			if(fd->held_pipe_lock)
 			{
 #ifndef WIN32