No other headers are included by mbedtls_config.h

These have been moved to build_info.h. Update the documentation to
reflect this.

Signed-off-by: Bence Szépkúti <bence.szepkuti@arm.com>
diff --git a/docs/3.0-migration-guide.d/split_config.md b/docs/3.0-migration-guide.d/split_config.md
index 9893261..6f433c5 100644
--- a/docs/3.0-migration-guide.d/split_config.md
+++ b/docs/3.0-migration-guide.d/split_config.md
@@ -9,7 +9,7 @@
 
 Also, if you have a custom configuration file:
 
-* Don't include `check_config.h` anymore.
+* Don't include `check_config.h` or `config_psa.h` anymore.
 * Don't define `MBEDTLS_CONFIG_H` anymore.
 
 A config file version symbol, `MBEDTLS_CONFIG_VERSION` was introduced.