Fix report feedback template fixture

* This was missed during the migration to Jinja 3.
* In Jinja 2.10, the parameter 'indentfirst' of function do_indent()
  was marked deprecated and a functionally identical 'first' was added.
* In Jinja 3.0, the deprecated functionality was removed, in this
  upstream commit:
  https://github.com/pallets/jinja/commit/b0015c72d5acbf93b9d99a1ce6167889338db85b

(Redmine issue: #7583)

lib/hawat/blueprints/reports/templates/reports/email_report_feedback.txt

@@ -9,7 +9,7 @@
 
 {{ _('Message by user:') | wordwrap }}
 
-{{ text | wordwrap(width=75, break_long_words=False) | indent(width=4, indentfirst=True) }}
+{{ text | wordwrap(width=75, break_long_words=False) | indent(width=4, first=True) }}
 
 {{ _('Link to report:') | wordwrap }}