fix(readme) update example 3 remove invalid argument

[juanpicado]

Description

Updates the example 3, the argument --validate-https and --allowed-schemes cannot be used together.

Types of changes

• [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 change)

Related Issue

Fix #89

Motivation and Context

How Has This Been Tested?

Screenshots (if appropriate):

Checklist:

• [x] I have updated the documentation (if required).
• [x] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes.
• [ ] All new and existing tests passed.
• [ ] I added a picture of a cute animal cause it's fun

[juanpicado]

I'm not 100% sure whether the explanation below the example also needs an update.

[lirantal]

Thanks Juan, this is great 👍