docs: drop "when does Robusta need internet" preamble from proxies page

https://claude.ai/code/session_019GQrc8wVq14if8f7F3pp4f

Author: claude

docs/setup-robusta/proxies.rst

@@ -1,11 +1,6 @@
 Deploying Behind Proxies
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-Robusta requires internet access in the following cases:
-
-* Robusta SaaS is enabled
-* Robusta is configured to send notifications to services such as Slack (via :ref:`sinks <sinks-reference>`)
-
 If your Kubernetes cluster is behind an HTTP proxy or firewall, follow the instructions below to ensure Robusta and HolmesGPT has the necessary access.
 
 Configuring Proxy Settings for Robusta