bug#73155: ruby-net-smtp-0.3.3 fails to build

[Tomás Ortín via Bug reports for GNU Guix]

`ruby-net-smtp` fails to build during the `check` phase, apparently due 
to an expired certificate. The certificate seems to be bundled with the 
package, so I suppose this means the package needs to be updated.

```
Error: test_enable_starttls(Net::TestSSLContext): 
OpenSSL::SSL::SSLError: SSL_connect returned=1 errno=0 
peeraddr=empty-path-AF_UNIX-sockaddr state=error: certificate verify 
failed (certificate has expired)
```