Update traefik image references to use %%IMAGE%% templating

(not sure how we missed these previously)

Author: tianon

traefik/content.md

@@ -29,7 +29,7 @@ Start Traefik v3:
 docker run -d -p 8080:8080 -p 80:80 \
   -v $PWD/traefik.yml:/etc/traefik/traefik.yml \
   -v /var/run/docker.sock:/var/run/docker.sock \
-  traefik:v3
+  %%IMAGE%%:v3
 ```
 
 Start a backend server using the `traefik/whoami` image:
@@ -89,7 +89,7 @@ Start Traefik v2:
 docker run -d -p 8080:8080 -p 80:80 \
 -v $PWD/traefik.yml:/etc/traefik/traefik.yml \
 -v /var/run/docker.sock:/var/run/docker.sock \
-traefik:v2.11
+%%IMAGE%%:v2.11
 ```
 
 Start a backend server using the `traefik/whoami` image: