Fix - dnspython version in requirements-dev.txt

[jbaptperez]

Description

The version of dnspython did not match the requirements.txt one.

Moreover, this dependency was already in requirements.txt and thus not necessary in requirements-dev.txt.

Type of change

Please delete options that are not relevant.

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes.

# No crash due to incompatibility of versions, only one dnspython dependency declaration.
pip install -r requirements.txt -r requirements-dev.txt

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [ ] I have made corresponding changes to the documentation
• [ ] I have added tests that prove my fix is effective or that my feature works

[elegantmoose]

Ty @jbaptperez