'/dev/stdout' does not exist on some systems (!)

The OVH VPS provider creates systems without /dev/stdout. I have never seen that before. But fine. We were passing it as a command line option to `openssl req`, but outputting to stdout is the default so it's not necessary to specify /dev/stdout.

Fixes #277. Also https://discourse.mailinabox.email/t/500-internal-server-error/475/10.

management/web_update.py

@@ -208,7 +208,6 @@ def create_csr(domain, ssl_key, env):
 	return shell("check_output", [
                 "openssl", "req", "-new",
                 "-key", ssl_key,
-                "-out",  "/dev/stdout",
                 "-sha256",
                 "-subj", "/C=%s/ST=/L=/O=/CN=%s" % (env["CSR_COUNTRY"], domain)])