Add missing "clone" in tests instructions

[bistory]

Hi, This is just a small fix in the "How to run tests?" section. The git command instruction is missing ;-)

[rbeuque74]

Hello @bistory, Thanks for your contribution.

Can you please follow the Contributions guildelines, especially the Developer Certificate of Origin.

Thanks, Romain

[rbeuque74]

Closing as no answer from the pull-request author. Feel free to reopen if it still applies

[bistory]

Yeah sorry but such a complete process for 5 added characters to fix the documentation is boring and useless... You can add them yourself, I don't need to get any attribution...