feat: remove support for deprecated postgresql version 11 (#372)

Author: Aashiq-J

tests/pr_test.go

@@ -92,7 +92,7 @@ func TestRunUpgradeCompleteExample(t *testing.T) {
 		BestRegionYAMLPath: regionSelectionPath,
 		ResourceGroup:      resourceGroup,
 		TerraformVars: map[string]interface{}{
-			"pg_version": "11", // Always lock to the lowest supported Postgres version
+			"pg_version": "12", // Always lock to the lowest supported Postgres version
 			"users": []map[string]interface{}{
 				{
 					"name":     "testuser",

variables.tf

@@ -28,10 +28,9 @@ variable "pg_version" {
       var.pg_version == "15",
       var.pg_version == "14",
       var.pg_version == "13",
-      var.pg_version == "12",
-      var.pg_version == "11"
+      var.pg_version == "12"
     ])
-    error_message = "Version must be 11, 12, 13, 14 or 15. If no value passed, the current ICD preferred version is used."
+    error_message = "Version must be 12, 13, 14 or 15. If no value passed, the current ICD preferred version is used."
   }
 }