Fix docs link

CL: Fix docs link

PUBLISHED_FROM=d1092fb9886740fd90912700dca19ca62d4c4091

Author: cpq

README.md

@@ -1,6 +1,6 @@
 # GATT Client RPC service
 
-Provides [RPC service](https://mongoose-os.com/docs/mos/userguide/rpc.md) for
+Provides [RPC service](https://mongoose-os.com/docs/mongoose-os/userguide/rpc.md) for
 [GATT](https://learn.adafruit.com/introduction-to-bluetooth-low-energy/gatt)
 client.