Fix CI YAML

The "extends" keyword is not yet in Gitlab 11.2 (it is said to be implemented
in 11.3…).

(cherry picked from commit f74e7261)

.gitlab-ci.yml

@@ -46,7 +46,7 @@ testsuite_matlab:
   dependencies:
     - build_binaries
 
-.testsuite_octave_template:
+.testsuite_octave_template: &testsuite_octave_definition
   stage: test
   variables:
     OPENBLAS_NUM_THREADS: 1
@@ -67,13 +67,13 @@ testsuite_matlab:
     - build_binaries
 
 testsuite_octave_auto:
-  extends: .testsuite_octave_template
+  <<: *testsuite_octave_definition
   only:
     - tags
     - schedules
 
 testsuite_octave_manual:
-  extends: .testsuite_octave_template
+  <<: *testsuite_octave_definition
   except:
     - tags
     - schedules