CI does not pass with julia 1.6, so test 1.7 instead

From the disscussion in the PR, it is not at all obvious to me
what the proper solution here is.

Author: LebedevRI

.github/workflows/CI.yml

@@ -23,7 +23,7 @@ jobs:
       fail-fast: false
       matrix:
         version:
-          - '1.6'
+          - '1.7'
           - '1'
           - pre
         os: