Remove openconext theme (#1994)

Remove unmaintained openconext theme

Prior to this change, the openconext theme was still there, but it was broken and unmaintained. Many twig variables were not set.
This change deprecates / removes the openconext theme that was succeeded by the new base and skeune themes in 2021.
 
Resolves #1980

Author: kayjoosten

.github/workflows/run-cypress.yml

@@ -45,10 +45,4 @@ jobs:
                     ' && \
                     docker compose exec -T cypress bash -c '
                       yarn install && cypress run --spec "cypress/integration/skeune/**/*.spec.js,cypress/integration/shared/*.spec.js" --browser=chrome --headless
-                    ' && \
-                    docker compose exec -T --user www-data engine.dev.openconext.local bash -c '
-                      EB_THEME=openconext ./theme/scripts/prepare-test.js
-                    ' && \
-                    docker compose exec -T cypress bash -c '
-                      cypress run --spec "cypress/integration/openconext/**/*.spec.js" --browser=chrome --headless
                     '

CHANGELOG.md

@@ -54,6 +54,8 @@ The following feedback pages previously returned HTTP **200 OK** and now return
 | `/authentication/feedback/invalid-acs-binding`        | 200    | 400   |
 | `/authentication/feedback/received-error-status-code` | 200    | 400   |
 
+Maintenance:
+* Removed the `openconext` theme. The `skeune` theme is now the only supported theme and the default. (#1980)
 
 ## UNRELEASED 7.2.0
 Upgrade to Symfony 7.4