left4me: drop redundant letsencrypt/domains from reactor

bundles/nginx/metadata.py auto-populates letsencrypt/domains from
nginx/vhosts.keys(). Declaring it again in the left4me reactor was a
no-op duplication. Removed; bw metadata still shows the same merged
state (left4.me with reload: [nginx]).

bundles/left4me/metadata.py

@@ -75,11 +75,12 @@ defaults = {
 
 @metadata_reactor.provides(
     'nginx/vhosts',
-    'letsencrypt/domains',
     'monitoring/services',
     'nftables/input',
 )
 def derived_from_domain(metadata):
+    # letsencrypt/domains is auto-populated from nginx/vhosts.keys() by
+    # bundles/nginx/metadata.py — don't duplicate it here.
     domain = metadata.get('left4me/domain')
     port_start = metadata.get('left4me/port_range_start')
     port_end = metadata.get('left4me/port_range_end')
@@ -95,11 +96,6 @@ def derived_from_domain(metadata):
                 },
             },
         },
-        'letsencrypt': {
-            'domains': {
-                domain: {},
-            },
-        },
         'monitoring': {
             'services': {
                 'left4me-web': {