create-realm: Simplify organization name field on new org form.

Removes the placeholder text and hint. Adds a link to the help
center article about creating your organization profile.

Fixes #34496.

tools/linter_lib/custom_check.py

@@ -569,7 +569,6 @@ html_rules: list["Rule"] = [
         "description": "`placeholder` value should be translatable.",
         "exclude_line": {
             ("templates/zerver/realm_creation_form.html", 'placeholder="acme"'),
-            ("templates/zerver/realm_creation_form.html", 'placeholder="Acme or Ακμή"'),
         },
         "exclude": {
             "templates/corporate",