added link to telemetry from admin page

Author: eugenio-sanchez-sg

docs/admin/index.mdx

@@ -31,6 +31,7 @@ Sourcegraph administration is primarily managed by site administrators, who are
 - [Beta and experimental features](/admin/beta_and_experimental_features)
 - [Code navigation](/code-search/code-navigation/)
 - [Pings](/admin/pings)
+- [Telemetry](/admin/telemetry)
 - [Enterprise pricing and licenses](/admin/subscriptions/)
 - [Search](/admin/search)
 - [Usage statistics](/admin/usage_statistics)