remove Julia 1.6

Author: jwahlstrand

.github/workflows/CI.yml

@@ -15,7 +15,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest, windows-latest, macOS-latest]
-        version: ['1.6', '1']
+        version: ['1']
         arch: [x64, x86]
         include:
           - os: ubuntu-latest