Mention LibNSS dependency for JA3

[DominoTree]

Update util-ja3.c

Update app-layer-ssl.c

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• I have read the contributing guide lines at https://redmine.openinfosecfoundation.org/projects/suricata/wiki/Contributing
• I have signed the Open Information Security Foundation contribution agreement at https://suricata-ids.org/about/contribution-agreement/
• I have updated the user guide (in doc/userguide/) to reflect the changes made (if applicable)

Link to redmine ticket:

Describe changes:

• Mention that required MD5 support is provided by LibNSS for JA3 (had to look at the code to figure out what additional library I needed)

PRScript output (if applicable):

[DominoTree]

Argh, tried to pull in upstream changes to avoid a merge conflict and I still ended up with one...

[victorjulien]

Merged in #4123, thanks Nick!