erp5_oauth_[google/facebook]_login: Drop minor duplication

See merge request !1607
13 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
passed ERP5.CodingStyleTest-Master

01:01:43

passed ERP5.PerformanceTest-Master

00:26:21

failed ERP5.UnitTest-Master

01:14:06

failed ERP5.UnitTest-Master.Medusa

01:35:34

passed SlapOS.Eggs.UnitTest-Master.Python2

00:13:49

passed SlapOS.Eggs.UnitTest-Master.Python3

00:15:59

passed SlapOS.Eggs.UnitTest-Master.Python2

00:13:51

passed SlapOS.Eggs.UnitTest-Master.Python2

00:17:11

passed SlapOS.Eggs.UnitTest-Master.Python2

00:15:08

passed SlapOS.Eggs.UnitTest-Master.Python2

00:13:30

passed SlapOS.Eggs.UnitTest-Master.Python3

00:17:55

passed SlapOS.Eggs.UnitTest-Master.Python3

00:15:36

passed SlapOS.Eggs.UnitTest-Master.Python3

00:13:33