ci: Test with Terraform 1.6.x (#335)

At some point we'll switch the CI workflows to using GitHub Actions shared configuration variables.

Author: bflad

.github/workflows/ci-go.yml

@@ -65,6 +65,7 @@ jobs:
           - '1.3.*'
           - '1.4.*'
           - '1.5.*'
+          - '1.6.*'
   terraform-provider-corner-tfprotov6:
     defaults:
       run:
@@ -103,6 +104,7 @@ jobs:
           - '1.3.*'
           - '1.4.*'
           - '1.5.*'
+          - '1.6.*'
   test:
     name: test (Go v${{ matrix.go-version }})
     runs-on: ubuntu-latest