Sphinx rendering warning due to missing newline
When rendering current master docs there will be the following warning from `sphinx`:
user@pc:~/suricata-update/doc$ make sphinx-build -b html -d _build/doctrees . _build/html Sphinx v4.1.2 in Verwendung making output directory... erledigt loading pickled environment... erledigt building [mo]: targets for 0 po files that are out of date building [html]: targets for 11 source files that are out of date updating environment: 0 added, 1 changed, 0 removed reading sources... [100%] add-source /home/user/suricata-update/doc/add-source.rst:30: WARNING: Unexpected indentation.
This is caused by a missing newline.
Sorry that was my fault on the last MR concerning the HTTP headers (#4362).