nimble/host: Fix Mesh feature description in syscfg.yml
nimble/host: Fix Mesh feature description in syscfg.yml

Reformulate the description text for BLE_MESH.

X-Original-Commit: 3fd472573892227fffad4def27517bc545d3a444

apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble