Add callouts to codehost connections docs (#959)

- https://sourcegraph.slack.com/archives/C079SAU0E72/p1738779930968759

Author: MaedahBatool

docs/admin/code_hosts/github.mdx

@@ -1,5 +1,9 @@
 # GitHub
 
+<TierCallout>
+  Supported on all Sourcegraph [pricing](https://sourcegraph.com/pricing) plans.
+</TierCallout>
+
 Site admins can sync Git repositories hosted on [GitHub.com](https://github.com) and [GitHub Enterprise](https://enterprise.github.com) with Sourcegraph so that users can search and navigate the repositories.
 
 There are 2 ways to connect with GitHub:

docs/admin/code_hosts/gitlab.mdx

@@ -1,5 +1,9 @@
 # GitLab
 
+<TierCallout>
+  Supported on Sourcegraph [Free](/pricing/free) and [Enterprise](/pricing/enterprise) plans.
+</TierCallout>
+
 Site admins can sync Git repositories hosted on [GitLab](https://gitlab.com) (GitLab.com and GitLab CE/EE) with Sourcegraph so that users can search and navigate the repositories.
 
 To connect GitLab to Sourcegraph:

docs/admin/code_hosts/index.mdx

@@ -1,5 +1,7 @@
 # Code host connections
 
+<Callout type="info">Sourcegraph Enterprise Starter supports only GitHub as a code host connection. Enterprise plan can connect to all supported code hosts listed on this page.</Callout>
+
 Sourcegraph can sync repositories from code hosts and other similar services. We designate code hosts between Tier 1 and Tier 2 based on Sourcegraph's capabilities when used with those code hosts.
 
 ## Tier 1 code hosts