feat: remove CustomizeDiff() func

This function is no longer needed, the issue it was addressing has been resolved by MS

microsoft/azure-container-apps#395

internal/services/containerapps/container_app_resource.go

@@ -405,35 +405,3 @@ func (r ContainerAppResource) Update() sdk.ResourceFunc {
 		},
 	}
 }
-
-func (r ContainerAppResource) CustomizeDiff() sdk.ResourceFunc {
-	return sdk.ResourceFunc{
-		Func: func(ctx context.Context, metadata sdk.ResourceMetaData) error {
-			if metadata.ResourceDiff != nil && metadata.ResourceDiff.HasChange("secret") {
-				stateSecretsRaw, configSecretsRaw := metadata.ResourceDiff.GetChange("secret")
-				stateSecrets := stateSecretsRaw.(*schema.Set).List()
-				configSecrets := configSecretsRaw.(*schema.Set).List()
-				// Check there's not less
-				if len(configSecrets) < len(stateSecrets) {
-					return fmt.Errorf("cannot remove secrets from Container Apps at this time due to a limitation in the Container Apps Service. Please see `https://github.com/microsoft/azure-container-apps/issues/395` for more details")
-				}
-				// Check secrets names in state are all present in config, the values don't matter
-				if len(stateSecrets) > 0 {
-					for _, s := range stateSecrets {
-						found := false
-						for _, c := range configSecrets {
-							if s.(map[string]interface{})["name"] == c.(map[string]interface{})["name"] {
-								found = true
-								break
-							}
-						}
-						if !found {
-							return fmt.Errorf("previously configured secret %q was removed. Removing secrets is not supported by the Container Apps Service at this time, see `https://github.com/microsoft/azure-container-apps/issues/395` for more details", s.(map[string]interface{})["name"])
-						}
-					}
-				}
-			}
-			return nil
-		},
-	}
-}