Remove support for old clone/fetch methods

Description

GitLab Runner now requires Refspec information in the job response to clone the project which is sent from a GitLab instance that is running version %11.9+

Proposal

Remove the old code which used to clone and fetch the repository

Links to related issues and merge requests / references

Main deprecation issue #3473 (closed) MR introducing new clone/fetch method !1203 (merged)