west.yml: Update mcumgr to backport fix for issue #38502#39658

cfriedt merged 1 commit intozephyrproject-rtos:v2.7-branchzephyrproject-rtos/zephyr:v2.7-branchfrom

de-nordic:mcumgr_backport-upstream-137-to-v2.7-branchde-nordic/zephyr:mcumgr_backport-upstream-137-to-v2.7-branchCopy head branch name to clipboard