Add missing annotation to the nbi charm

Change-Id: I85aa5d066eb7e18995a22c1cc2e9a5fe6f021dd7
Signed-off-by: David Garcia <david.garcia@canonical.com>
diff --git a/installers/charm/nbi/src/pod_spec.py b/installers/charm/nbi/src/pod_spec.py
index 4bbe334..105e877 100644
--- a/installers/charm/nbi/src/pod_spec.py
+++ b/installers/charm/nbi/src/pod_spec.py
@@ -298,7 +298,8 @@
     annotations = {
         "nginx.ingress.kubernetes.io/proxy-body-size": "{}".format(
             max_file_size + "m" if max_file_size > 0 else max_file_size
-        )
+        ),
+        "nginx.ingress.kubernetes.io/backend-protocol": "HTTPS",
     }
 
     if ingress_whitelist_source_range: