cloud: clarify enterprise vpn (#1256)

address confusion here
https://sourcegraph.slack.com/archives/C03JR7S7KRP/p1752178244994739?thread_ts=1752102734.432259&cid=C03JR7S7KRP

## Pull Request approval

na

Author: michaellzc

docs/cloud/index.mdx

@@ -2,7 +2,7 @@
 
 Sourcegraph Cloud is a single-tenant cloud solution. Cloud instances are private, dedicated instances provisioned and managed by Sourcegraph. Sourcegraph Cloud was formerly known as managed instances.
 
-Sourcegraph provisions each instance in an isolated and secure cloud environment. Access is restricted to only your organization through your SSO provider of choice. Enterprise VPN is available upon request.
+Sourcegraph provisions each instance in an isolated and secure cloud environment. Access is restricted to only your organization through your SSO provider of choice. Additionally, we can restrict access to your Sourcegraph Cloud instance to authorized IP addresses upon request, e.g., exit gateway of corporate vpn.
 
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