OpenVPN v2.6.3 release

2023.04.13 -- Version 2.6.3

Frank Lichtenheld (3):
      GHA: remove Ubuntu 18.04 builds
      vcpkg: request "tools" feature of openssl for MSVC build
      doc: run rst2* with --strict to catch warnings

Lev Stipakov (1):
      Support of DNS domain for DHCP-less drivers

Selva Nair (1):
      Bug-fix: segfault in dco_get_peer_stats()