Update CI.yml to add lts release

Author: ericqu

.github/workflows/CI.yml

@@ -19,7 +19,7 @@ jobs:
       fail-fast: false
       matrix:
         version:
-          - '1.6'
+          - '1.6.7' # lts release
           - '1' # automatically expands to the latest stable 1.x release of Julia.
         os:
           - ubuntu-latest