cmd/admingolangorg: force https for all paths

Change-Id: I1013687b302d9ddc5005c9ad80d3295b3ee461f4
Reviewed-on: https://go-review.googlesource.com/c/website/+/244338
Run-TryBot: Andrew Bonventre <andybons@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alexander Rakoczy <alex@golang.org>

cmd/admingolangorg/app.yaml

@@ -8,6 +8,7 @@ env_variables:
 handlers:
   - url: .*
     script: auto
+    secure: always
     login: admin # THIS MUST BE SET
 
 vpc_access_connector: