osslsigncode: roll back to working version

The `osslsigncode.exe` binary was updated last night, as part of a huge
OpenSSL rebuild that apparently changed _something_ in the DLL.

This matters because Git for Windows builds its own versions of the
OpenSSL packages (so as to fulfill the promise of limited i686 support),
and since that update the `osslsigncode.exe` binary no longer works
with the OpenSSL DLLs of Git for Windows, failing with an exit code 127
(or more precisely, with 0xC0000139).

This close to Git for Windows v2.53, let's just force the
`osslsigncode.exe` back to a version we know works with Git for Windows'
OpenSSL DLLs.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho