feat: add to keyword set client cert, cert as tuple type

[alraoul]

While trying to update requests library from version 2.31.0 to the latest version 2.32.3 we are facing following issue due to the fact that the requests library now on take cert parameter as tuple and not list anymore:

TypeError: unhashable type: 'list'
Steps to reproduce:

Working scenario with requests 2.31.0
${paths_list} = Create List ${CURDIR}/client.crt ${CURDIR}/client.key
Set Client Cert ${paths_list}
POST https://localhost:8080/test
Failing scenario with requests 2.32.3
${paths_list} = Create List ${CURDIR}/client.crt ${CURDIR}/client.key
Set Client Cert ${paths_list}
POST https://localhost:8080/test
failing with error TypeError: unhashable type: 'list'
Solution - enhanced keyword "Set Client Cert" to take as cert parameter a tuple too (which will be use in the background by the requests post function)

[asyrjasalo]

That's clear. Thank You.