chore(cliff): fix heading level for new contributors (#425)

Author: tessus

cliff.toml

@@ -35,15 +35,14 @@ body = """
 {% endfor %}
 
 {%- if github.contributors | filter(attribute="is_first_time", value=true) | length != 0 %}
-  ## New Contributors
+    ### New Contributors
 {%- endif -%}
-
 {% for contributor in github.contributors | filter(attribute="is_first_time", value=true) %}
-  * @{{ contributor.username }} made their first contribution
-    {%- if contributor.pr_number %} in \
-      [#{{ contributor.pr_number }}]({{ self::remote_url() }}/pull/{{ contributor.pr_number }}) \
-    {%- endif %}
-{%- endfor %}\n
+        - @{{ contributor.username }} made their first contribution
+            {%- if contributor.pr_number %} in \
+            [#{{ contributor.pr_number }}]({{ self::remote_url() }}/pull/{{ contributor.pr_number }}) \
+            {%- endif %}
+{%- endfor %}\n\n
 """
 # template for the changelog footer
 footer = """