ci: Remove OpenBSD

There once was OpenBSD CI from sr.ht sponsored by wstrm.
It's not available since a log time. So let's drop it.

.builds/openbsd.yml

@@ -1,49 +0,0 @@
-image: openbsd/7.0
-
-packages:
-  - gcc-11.2.0p0
-  - cmake
-  - gmake
-  - cmocka
-  - libtool
-  - automake-1.16.3
-  - pkgconf
-  - readline
-  - python-3.8.12
-  - autoconf-2.69p3
-  - autoconf-archive
-  - curl
-  - gpgme
-  - glib2
-  - gtk+2
-  - libotr
-  - libassuan
-  - libgpg-error
-  - libgcrypt
-  - libsignal-protocol-c
-  - sqlite3
-
-sources:
-  - https://github.com/strophe/libstrophe.git#0.11.0
-  - https://github.com/profanity-im/profanity
-
-environment:
-  LANG: en_US.UTF-8
-
-tasks:
-  - symlink: |
-      doas ln -sf /usr/local/bin/python3 /usr/local/bin/python
-      doas ln -sf /usr/local/bin/python3-config /usr/local/bin/python-config
-      doas ln -sf /usr/local/bin/pydoc3  /usr/local/bin/pydoc
-  - build: |
-      export AUTOCONF_VERSION=2.69
-      export AUTOMAKE_VERSION=1.16
-
-      cd ~/libstrophe
-      ./bootstrap.sh
-      ./configure
-      make
-      doas make install
-
-      cd ~/profanity
-      ./ci-build.sh