The docs say it should be released in the last CryptMsgUpdate, but tests show
it's actually released in CryptMsgClose. So let's do the same.
This solve a use-after-free issue for signed messages, because they contains
HCRYPTHASH objects which references the context internally, and will use it
in CryptDestroyHash. If the context is released in CSignedEncodeMsg_Open, this
will be a use-after-free.
--
v2: crypt32: Don't release context in CSignedEncodeMsg_Open.
https://gitlab.winehq.org/wine/wine/-/merge_requests/8376