Compress doc images

...troubleshooting/img/GoogleWorkspace-basic-SAML_v14_10.png

...ion/troubleshooting/img/GoogleWorkspace-claims_v14_10.png

.../troubleshooting/img/GoogleWorkspace-linkscert_v14_10.png

doc/integration/img/limit_namespaces_projects_options.png

doc/subscriptions/img/support_diagram_c.png

doc/tutorials/img/branches_dropdown_v14_10.png

...stream_analytics/img/vsa_aggregated_data_toggle_v14_9.png

.../project/import/img/gitlab_import_history_page_v14_10.png

doc/user/project/issues/img/design_management_v14_10.png

...merge_requests/approvals/img/security_approvals_v15_0.png