fix: hide "Create Workspace" button for deleted templates (#22092)

**Background**

Reported in #17417, there is a `deleted` query parameter supported by
/api/v2/templates, but we do not respect this field on the client,
showing the "Create Workspace" button for deleted templates.

**Expected Behavior**

Don't show the "Create Workspace" button for deleted templates.

**Notes**

This PR adds a new `deleted` field to the templates API response.

Co-authored-by: Danielle Maywood <danielle@themaywoods.com>

coderd/apidoc/docs.go

@@ -18919,6 +18919,9 @@ const docTemplate = `{
                 "default_ttl_ms": {
                     "type": "integer"
                 },
+                "deleted": {
+                    "type": "boolean"
+                },
                 "deprecated": {
                     "type": "boolean"
                 },

coderd/apidoc/swagger.json

@@ -17306,6 +17306,9 @@
 				"default_ttl_ms": {
 					"type": "integer"
 				},
+				"deleted": {
+					"type": "boolean"
+				},
 				"deprecated": {
 					"type": "boolean"
 				},