docs: clarify the join behaviour change in the changelog (#2714)

Author: tatomyr

docs/@v2/changelog.md

@@ -589,7 +589,8 @@ toc:
 
 - Fixed an issue where the root config was not properly merged with the `apis` config.
 - Resolved an issue that caused configuration parsing to fail when the config value was set to `null`.
-- Improved join command server handling for specifications with differing servers.
+- Improved `join` command server handling for specifications with differing servers.
+  **Warning**: this change may break workflows that relied on root-level server inheritance.
 - Updated @redocly/respect-core to v2.0.5.
 
 ## 2.0.4 (2025-08-12)

packages/cli/CHANGELOG.md

@@ -582,7 +582,8 @@
 
 - Fixed an issue where the root config was not properly merged with the `apis` config.
 - Resolved an issue that caused configuration parsing to fail when the config value was set to `null`.
-- Improved join command server handling for specifications with differing servers.
+- Improved `join` command server handling for specifications with differing servers.
+  **Warning**: this change may break workflows that relied on root-level server inheritance.
 - Updated @redocly/respect-core to v2.0.5.
 
 ## 2.0.4