fix: remove comma-delimited joining of characters on model_card_authors and model_card_contact

In this PR we remove `join(', ')` for both the `model_card_authors` and `model_card_contact` in `language_model_template1.md`. What the join does is for e.g. an author name `Jane Doe`, displays it as `J, a, n, e, , D, o, e`, which is clearly not what we want. Technically instead of a join there should be a `split(',')` but it's probably an overkill and enough to just display names and contacts as-is.

language_model_template1.md

@@ -311,11 +311,11 @@ Carbon emissions can be estimated using the [Machine Learning Impact calculator]
 
 <!-- This section provides another layer of transparency and accountability. Whose views is this model card representing? How many voices were included in its construction? Etc. -->
 
-{{ model_card_authors | join(', ') | default("More information needed", true)}}
+{{ model_card_authors | default("More information needed", true)}}
 
 # Model Card Contact
 
-{{ model_card_contact | join(', ') | default("More information needed", true)}}
+{{ model_card_contact | default("More information needed", true)}}
 
 # How to Get Started with the Model