Update nginx from 1.18.0 to 1.19.0.

<ChangeLog>

*) Feature: client certificate validation with OCSP.

*) Bugfix: "upstream sent frame for closed stream" errors might occur

when working with gRPC backends.

*) Bugfix: OCSP stapling might not work if the "resolver" directive was

not specified.

*) Bugfix: connections with incorrect HTTP/2 preface were not logged.

</ChangeLog>