template tags: don't support getting producer from label anymore

(this was required when we only got labels and zero details from
data.grandlyon (see #19294))

combo_plugin_gnm/templatetags/gnm.py

@@ -474,8 +474,6 @@ def as_producer(slug):
 
     if slug.startswith('_'):
         producer = slug.split('_')[1].replace('hobo-', '')
-    else:
-        producer = slugify(slug)
 
     if slug == 'eservices':
         # handle collectivity sites, they are individually named