Update disk type schema field to support db-c4a-highmem-4 tier (#13236) (#22485)

[upstream:f0f9f81a76c7cd8acd855bf556b0eab7abfa7632]

Signed-off-by: Modular Magician <[email protected]>

Author: modular-magician

.changelog/13236.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+sql: the Terraform-based default value for `settings.disk_type` in `google_sql_database_instance` has been replaced with server-assigned default, allowing for compatibility with machine types that require `HyperDisk_Balanced`
+```

google/services/sql/resource_sql_database_instance.go

@@ -428,10 +428,10 @@ is set to true. Defaults to ZONAL.`,
 						"disk_type": {
 							Type:             schema.TypeString,
 							Optional:         true,
-							Default:          "PD_SSD",
+							Computed:         true,
 							ForceNew:         true,
 							DiffSuppressFunc: caseDiffDashSuppress,
-							Description:      `The type of data disk: PD_SSD, PD_HDD, or HYPERDISK_BALANCED. Defaults to PD_SSD.`,
+							Description:      `The type of supported data disk is tier dependent and can be PD_SSD or PD_HDD or HyperDisk_Balanced `,
 						},
 						"ip_configuration": {
 							Type:     schema.TypeList,

google/services/sql/resource_sql_database_instance_test.go

@@ -1706,7 +1706,7 @@ func TestAccSQLDatabaseInstance_DefaultEdition(t *testing.T) {
 	t.Parallel()
 	databaseName := "tf-test-" + acctest.RandString(t, 10)
 	databaseVersion := "POSTGRES_16"
-	enterprisePlusTier := "db-perf-optimized-N-2"
+	enterprisePlusTier := "db-c4a-highmem-4"
 	acctest.VcrTest(t, resource.TestCase{
 		PreCheck:                 func() { acctest.AccTestPreCheck(t) },
 		ProtoV5ProviderFactories: acctest.ProtoV5ProviderFactories(t),