tools: buildman: Fix doc path in warning message

Fix documentation path in deprecated warning message about device
driver.

Signed-off-by: Johannes Krottmayer <krjdev@gmail.com>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/tools/buildman/test.py b/tools/buildman/test.py
index 714bb3e..2728743 100644
--- a/tools/buildman/test.py
+++ b/tools/buildman/test.py
@@ -37,7 +37,7 @@
 This board does not use CONFIG_DM. CONFIG_DM will be
 compulsory starting with the v2020.01 release.
 Failure to update may result in board removal.
-See doc/driver-model/migration.rst for more info.
+See doc/develop/driver-model/migration.rst for more info.
 ====================================================
 '''