docs: fix firewall_resource examples input parameters (#557)

In the example, we should use `firewall` instead of `name` as per the
options described at the top of the documentation.

plugins/modules/firewall_resource.py

@@ -48,30 +48,30 @@
 EXAMPLES = """
 - name: Apply a firewall to a list of servers
   hetzner.hcloud.firewall_resource:
-    name: my-firewall
+    firewall: my-firewall
     servers:
       - my-server
       - 3456789
     state: present
 
 - name: Remove a firewall from a list of servers
   hetzner.hcloud.firewall_resource:
-    name: my-firewall
+    firewall: my-firewall
     servers:
       - my-server
       - 3456789
     state: absent
 
 - name: Apply a firewall to resources using label selectors
   hetzner.hcloud.firewall_resource:
-    name: my-firewall
+    firewall: my-firewall
     label_selectors:
       - env=prod
     state: present
 
 - name: Remove a firewall from resources using label selectors
   hetzner.hcloud.firewall_resource:
-    name: my-firewall
+    firewall: my-firewall
     label_selectors:
       - env=prod
     state: absent