Use Julia v1.6 to generate docs.

Author: sunoru

.github/workflows/ci.yml

@@ -36,7 +36,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        julia-version: ["1.3"]
+        julia-version: ["1.6"]
         julia-arch: [x64]
         os: [ubuntu-latest]
     steps: