server.py tries to launch a matrix_sso_helper binary when connecting to
a homeserver that uses some SSO mechanism instead of plain login and
password, but doesn't have $out/bin in $PATH.
Using substituteInPlace to patch server.py so that the helper process is
started by using its actual filesystem location instead of relying on
$PATH.
Fixes: https://github.com/NixOS/nixpkgs/issues/124186
(cherry picked from commit f7ccc5f35d0e1fe11a7e01e3dddd1ff28566ba1d)
ac93a00745