Fix license typo

[adipierro]

Please sign (check) the below before submitting the Pull Request:

• I have signed the ntop Contributor License Agreement at https://github.com/ntop/legal/blob/main/individual-contributor-licence-agreement.md
• I have read the contributing guidelines at https://github.com/ntop/nDPI/blob/dev/CONTRIBUTING.md
• I have updated the documentation (in doc/) to reflect the changes made (if applicable)

Link to the related issue:

Describe changes:

Fixed a possible typo (if not a joke about Redis adopting dual-license), which might have been caused by mass-replacing redis with zmq, affecting word 'redistribute' in license header of some protocol dissector files.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[IvanNardi]

Good catch. Likely some kind of joke when the ZMQ code has been added for the first time 10 years ago...
Thanks!