west: move to version v0.5.7

This fixes some high priority issues, including syntax errors in
docstrings which prevent us from including API docs in our Sphinx
tree.

Signed-off-by: Marti Bolivar <[email protected]>

Author: Marti Bolivar

west.yml

@@ -16,7 +16,7 @@
 
 west:
   url: https://github.com/zephyrproject-rtos/west
-  revision: v0.5.6
+  revision: v0.5.7
 
 manifest:
   defaults: