Change obmc-ubi-fs to distro feature

obmc-ubi-fs is moving to a distro feature, update the
ubi-code-update.md doc to reflect this.
https://gerrit.openbmc-project.xyz/#/c/9493

Change-Id: I8f3a3e9f9cf3ddb0846cb9f1b0a7877e9c4e50b9
Signed-off-by: Gunnar Mills <gmills@us.ibm.com>
diff --git a/code-update/ubi-code-update.md b/code-update/ubi-code-update.md
index 9b2cfc8..ceb056b 100644
--- a/code-update/ubi-code-update.md
+++ b/code-update/ubi-code-update.md
@@ -5,7 +5,7 @@
 
  * Static, non-UBI layout - The default code update
 
- * UBI layout - enabled via obmc-ubi-fs machine feature
+ * UBI layout - enabled via `obmc-ubi-fs` distro feature
 
 This document describes the UBI code update. The non-UBI code update can be
 found here: [code-update.md](code-update.md)