chore: Update coder/coder provider in example templates (#3581)

Additionally, a convenience script was added to
`examples/update_template_versions.sh` to keep the templates up-to-date.

Fixes #2966

examples/templates/docker-code-server/main.tf

@@ -2,7 +2,7 @@ terraform {
   required_providers {
     coder = {
       source  = "coder/coder"
-      version = "0.4.5"
+      version = "0.4.9"
     }
     docker = {
       source  = "kreuzwerker/docker"