Strip ANSI escape codes from logs in CloudWatch (#9)

Now that we are included step logs, we need to strip the colour escape
sequences.
diff --git a/cloud-init.yml b/cloud-init.yml
index e65b954..9b2f9f5 100644
--- a/cloud-init.yml
+++ b/cloud-init.yml
@@ -288,6 +288,7 @@
 
           if err == null {
             . = merge(., structured)
+            .message = strip_ansi_escape_codes!(.message)
             .type = "job-output"
           }
         '''