Remove unused fields in synthetic_monitoring_installation (#966)

* Remove unused fields in `synthetic_monitoring_installation`

* Remove update mapping

Author: julienduchesne

docs/resources/synthetic_monitoring_installation.md

@@ -58,8 +58,6 @@ provider "grafana" {
 
 ### Optional
 
-- `logs_instance_id` (Number, Deprecated) Deprecated: Not used anymore.
-- `metrics_instance_id` (Number, Deprecated) Deprecated: Not used anymore.
 - `stack_sm_api_url` (String) The URL of the SM API to install SM on. This depends on the stack region, find the list of API URLs here: https://grafana.com/docs/grafana-cloud/synthetic-monitoring/private-probes/#probe-api-server-url. A static mapping exists in the provider but it may not contain all the regions. If it does contain the stack's region, this field is computed automatically and readable.
 
 ### Read-Only

internal/resources/cloud/resource_synthetic_monitoring_installation.go

@@ -44,7 +44,6 @@ This resource cannot be imported but it can be used on an existing Synthetic Mon
 `,
 		CreateContext: ResourceInstallationCreate,
 		ReadContext:   ResourceInstallationRead,
-		UpdateContext: ResourceInstallationRead,
 		DeleteContext: ResourceInstallationDelete,
 
 		Schema: map[string]*schema.Schema{
@@ -68,18 +67,6 @@ This resource cannot be imported but it can be used on an existing Synthetic Mon
 				ForceNew:    true,
 				Description: "The ID or slug of the stack to install SM on.",
 			},
-			"metrics_instance_id": {
-				Type:        schema.TypeInt,
-				Optional:    true,
-				Deprecated:  "Not used anymore.",
-				Description: "Deprecated: Not used anymore.",
-			},
-			"logs_instance_id": {
-				Type:        schema.TypeInt,
-				Optional:    true,
-				Deprecated:  "Not used anymore.",
-				Description: "Deprecated: Not used anymore.",
-			},
 			"sm_access_token": {
 				Type:        schema.TypeString,
 				Computed:    true,