IBX-10312: Rebranded VCL files (#42)

Rename backend to correspond to ibexa/http-cache#64

Author: adriendupuis

docker/entrypoint/varnish/parameters.vcl

@@ -1,6 +1,6 @@
 // Custom parameters.vcl for docker use
 
-backend ezplatform {
+backend ibexa {
     .host = "web";
     .port = "80";
 }