ERP5TypeTestCase: drop support for http repositories in tests

this only supported http and never supported https, probably nobody is
using this and it makes porting to python3 more complicated
4 jobs for for_testrunner_2 in 0 seconds
Status Job ID Name Coverage
  External
passed ERP5.CodingStyleTest-TestRunner2

01:39:17

failed ERP5.UnitTest-TestRunner2

03:30:24

passed ERP5.CodingStyleTest-TestRunner2

01:46:26

failed ERP5.UnitTest-TestRunner2

04:23:02