CCM-8590: add env var to workflows

Author: alexnuttall

.github/workflows/stage-2-test.yaml

@@ -35,6 +35,7 @@ on:
 env:
   AWS_REGION: eu-west-2
   TERM: xterm-256color
+  ENABLE_LETTERS: true
 
 permissions:
   id-token: write # This is required for requesting the JWT

.github/workflows/stage-4-acceptance.yaml

@@ -34,6 +34,7 @@ on:
 
 env:
   AWS_REGION: eu-west-2
+  ENABLE_LETTERS: true
 
 permissions:
   id-token: write # This is required for requesting the JWT