julia 1.6 and 1.9 instead of 1.7

.gitlab-ci.yml

@@ -16,8 +16,12 @@
         c, t = get_summary(process_folder())
         using Printf
         @printf "Test coverage %.2f%%\n" 100c / t'
-Julia 1.7:
-  image: julia:1.7
+Julia 1.6:
+  image: julia:1.6
+  extends:
+    - .script
+Julia 1.9:
+  image: julia:1.9
   extends:
     - .script
     - .coverage