update images and refs and remove old image files (#18731)

content/admin/_index.md

@@ -18,7 +18,7 @@ grid:
 
 The [Docker Admin](https://admin.docker.com) console provides administrators with centralized observability, access management, and controls for their company and organizations. To provide these features, Docker uses the following hierarchy and roles.
 
-![Docker hierarchy](./images/docker-admin-structure.png)
+![Docker hierarchy](./images/docker-admin-structure.webp)
 
 - Company: A company simplifies the management of Docker organizations and settings. Creating a company is optional and only available to Docker Business subscribers.
   - Company owner: A company can have multiple owners. Company owners have company-wide observability and can manage company-wide settings that apply to all associated organizations. In addition, company owners have the same access as organization owners for all associated organizations.

content/includes/admin-company-overview.md

@@ -2,7 +2,7 @@ A company provides a single point of visibility across multiple organizations. T
 
 The following diagram depicts the setup of a company and how it relates to associated organizations.
 
-![company-hierarchy](/admin/images/docker-admin-structure.png)
+![company-hierarchy](/admin/images/docker-admin-structure.webp)
 
 ## Key features
 

content/includes/admin-org-overview.md

@@ -11,4 +11,4 @@ organization.
 
 The following diagram depicts the setup of an organization and how it relates to teams. Teams are an optional feature that owners can use to group members and assign permissions.
 
-![organization-hierarchy](/admin/images/org-structure.png)
+![organization-hierarchy](/admin/images/org-structure.webp)