Add shellcheck exclusion

Signed-off-by: Jacob Woffenden <jacob.woffenden@digital.justice.gov.uk>

Author: Jacob Woffenden

features/src/kubernetes/install-kubernetes-cli.sh

@@ -2,6 +2,8 @@
 
 set -e
 
+# shellcheck source=/dev/null
+# file not accessible until being built
 source /usr/local/bin/devcontainer-utils
 
 get_system_architecture