fix: updated icon for cmux module (#531)

## Description

<!-- Briefly describe what this PR does and why -->

## Type of Change

- [ ] New module
- [ ] New template
- [ ] Bug fix
- [x] Feature/enhancement
- [ ] Documentation
- [ ] Other

## Module Information

**Path:** `registry/coder/modules/cmux`  
**New version:** `v1.0.1`  
**Breaking change:** [ ] Yes [ ] No

## Testing & Validation

- [x] Tests pass (`bun test`)
- [x] Code formatted (`bun fmt`)
- [x] Changes tested locally

registry/coder/modules/cmux/main.tf

@@ -110,7 +110,7 @@ variable "open_in" {
 resource "coder_script" "cmux" {
   agent_id     = var.agent_id
   display_name = "cmux"
-  icon         = "/icon/terminal.svg"
+  icon         = "/icon/cmux.svg"
   script = templatefile("${path.module}/run.sh", {
     VERSION : var.install_version,
     PORT : var.port,
@@ -134,7 +134,7 @@ resource "coder_app" "cmux" {
   slug         = var.slug
   display_name = var.display_name
   url          = "http://localhost:${var.port}"
-  icon         = "/icon/terminal.svg"
+  icon         = "/icon/cmux.svg"
   subdomain    = var.subdomain
   share        = var.share
   order        = var.order