Add TF 1.9 to tested versions, remove 1.6

.github/workflows/test.yml

@@ -66,9 +66,9 @@ jobs:
       matrix:
         # list whatever Terraform versions here you would like to support
         terraform:
-          - '1.6.*'
           - '1.7.*'
           - '1.8.*'
+          - '1.9.*'
     steps:
       - uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1
       - uses: actions/setup-go@0c52d547c9bc32b1aa3301fd7a9cb496313a4491 # v5.0.0