Do not use constraints when preparing venv for k8s tests on CI

When k8s virtualenv is prepared to run k8s tests we are using
constraints, this however might lead to a problem when we increase
minimum version of an affected dependency and it conflicts with
the constraints stored in main.

Therefore in case we run tests in CI (which is indicated by
specific pull tag that we use) we do not use constraints for
installing the kubernetes venv. It should be fine, as we are
pretty much running this only as a vehicle to run tests.

scripts/ci/kubernetes/ci_run_kubernetes_tests.sh

@@ -89,11 +89,19 @@ function create_virtualenv() {
 
     pip install --upgrade "pip==${AIRFLOW_PIP_VERSION}" "wheel==${WHEEL_VERSION}"
 
-    pip install pytest freezegun \
-      --constraint "https://raw.githubusercontent.com/${CONSTRAINTS_GITHUB_REPOSITORY}/${DEFAULT_CONSTRAINTS_BRANCH}/constraints-${HOST_PYTHON_VERSION}.txt"
+    local constraints=(
+        --constraint
+        "https://raw.githubusercontent.com/${CONSTRAINTS_GITHUB_REPOSITORY}/${DEFAULT_CONSTRAINTS_BRANCH}/constraints-${HOST_PYTHON_VERSION}.txt"
+    )
+    if [[ -n ${GITHUB_REGISTRY_PULL_IMAGE_TAG=} ]]; then
+        # Disable constraints when building in CI with specific version of sources
+        # In case there will be conflicting constraints
+        constraints=()
+    fi
+
+    pip install pytest freezegun "${constraints[@]}"
 
-    pip install -e ".[cncf.kubernetes,postgres]" \
-      --constraint "https://raw.githubusercontent.com/${CONSTRAINTS_GITHUB_REPOSITORY}/${DEFAULT_CONSTRAINTS_BRANCH}/constraints-${HOST_PYTHON_VERSION}.txt"
+    pip install -e ".[cncf.kubernetes,postgres]" "${constraints[@]}"
 }
 
 function run_tests() {