ext_conf_template.txt: unify naming flag production

extension/ext_conf_template.txt

-# cat=config/config; type=string; label=Marks a production installation:Possible values: 'yes', 'no'. Retrieve via '{{flagProduction:Y}}''.  Default is 'yes'. Used to differentiate between development & production systems.
+# cat=config/config; type=string; label=Flag Production:Possible values: 'yes', 'no'. Retrieve via '{{flagProduction:Y}}''.  Default is 'yes'. Used to differentiate between development & production systems.
 flagProduction = yes
 
 # cat=config/config; type=string; label=Max file size for file uploads:If empty, take minimum of 'post_max_size' and 'upload_max_filesize' (PHP.INI).