chore: remove speakers field

Most people will not have reliable data and we do not want to maintain this.

Author: nijel

.github/ISSUE_TEMPLATE/language_request.yml

@@ -57,13 +57,6 @@ body:
     description: List any non-standard, legacy, or common alternate codes that should map to this language.
     placeholder: |
       old_code -> tok
-- type: textarea
-  id: population
-  attributes:
-    label: Speaker or population source
-    description: If available, provide a speaker count and source link.
-    placeholder: |
-      12345 speakers, source:
 - type: textarea
   id: additional
   attributes: