Docs: update SAML IdP GCP workforce guide with IAM role prerequisite and new input label copy

docs/pages/access-controls/idps/saml-gcp-workforce-identity-federation.mdx

@@ -27,6 +27,8 @@ SAML IdP, so users can sign in into GCP web console by authenticating with Telep
 Reference](./saml-reference.mdx) before proceeding.
 - User with permission to create service provider resource. The preset `editor` role has this permission.
 - Access to GCP IAM API, with permission to create workforce identity pool, pool provider and an IAM policy.
+At a minimum, both the "IAM Workforce Pool Admin" and "Organization Viewer" [GCP roles](https://cloud.google.com/iam/docs/configuring-workforce-identity-federation#required-roles)
+are required (assigned at the GCP organization level) to configure GCP Workforce Identity Federation.
 
 
 Teleport Web UI offers both the guided and manual configuration flow for GCP Workforce Identity
@@ -47,15 +49,15 @@ Now follow the steps listed below.
 ## Step 1/3. Configure workforce pool
 As a first step, provide the following information to the script generator.
 
-![Test the IdP](../../../img/access-controls/saml-idp/gcp-workforce/generate-script.png)
+![Test the IdP](../../../img/access-controls/saml-idp/gcp-workforce/generate-command.png)
 - **Organization ID:** Organization ID of GCP account. The ID is required to create a workforce pool.
-- **Pool Name:** Name of the workforce pool to be created. Name should follow [GCP resource naming
+- **Workforce pool name:** Name of the workforce pool to be created. Name should follow [GCP resource naming
 convention](https://cloud.google.com/compute/docs/naming-resources#resource-name-format).
-- **Pool Provider Name:** Name of the workforce pool provider to be created. Pool provider name
-will also be used as SAML service provider name in the next step. Name should follow
+- **App name - Workforce pool provider name:** SAML app name. The name
+will also be used as a workforce pool provider name in the GCP. Name should follow
 [GCP resource naming convention](https://cloud.google.com/compute/docs/naming-resources#resource-name-format).
 
-Click on **Generate Script** button. Teleport Web UI will now show you a copyable bash script.
+Click on the **Generate Command** button. The Teleport Web UI will now show you a copyable bash script.
 
 Open GCP [Cloud Shell](https://shell.cloud.google.com/?show=terminal) and inside the Cloud Shell terminal,
 paste the bash script you copied above.