Remove unneeded assignment in PyBytes_Concat() (GH-15274)


The `wb.len = -1` assignment is unneeded since its introduction in 161d695fb0455ce52530d4f43a9eac4c738f64bb as `PyObject_GetBuffer` always fills it in.
(cherry picked from commit afdeb189e97033b54cef44a7490d89d2013cb4e5)

Co-authored-by: Sergey Fedoseev <fedoseev.sergey@gmail.com>
1 file changed