Drop tests on SQLServer 2019

The preview version of SQLServer 2019 has an expiration period. Let's
wait for the GA release instead of upgrading preview versions from
time to time.

.cirrus.yml

@@ -262,41 +262,6 @@ test_sql_mssql2017_task:
       path: "**/test-results/**/*.xml"
       format: junit
 
-test_sql_mssql2019_task:
-  depends_on: build
-  # Comment the following line and commit with message "DO NOT MERGE" in order to run
-  # this task on your branch
-  only_if: $CIRRUS_TAG == "nightly-build"
-  gke_container:
-    image: gradle:5.4.1-jdk11
-    cluster_name: cirrus-euw3a-cluster
-    zone: europe-west3-a
-    namespace: default
-    cpu: 1
-    memory: 5Gb
-    additional_containers:
-      - name: mssql
-        image: mcr.microsoft.com/mssql/server:2019-CTP2.2-ubuntu
-        port: 1433
-        cpu: 2
-        memory: 5Gb
-        env:
-          MSSQL_PID: Developer # this is the default edition
-          ACCEPT_EULA: Y
-          SA_PASSWORD: sonarqube!1
-  gradle_cache:
-    folder: ~/.gradle/caches
-  script:
-    - ./private/cirrus/cirrus-db-unit-test.sh mssql2019
-  cleanup_before_cache_script:
-    - ./private/cirrus/cleanup-gradle-cache.sh
-  on_failure:
-    reports_artifacts:
-      path: "**/build/reports/**/*"
-    junit_artifacts:
-      path: "**/test-results/**/*.xml"
-      format: junit
-
 
 # this is the oldest compatible version of PostgreSQL
 test_sql_postgres93_task: