clarify error message

Author: lzrd

gateway-messages/src/sp_to_mgs.rs

@@ -1344,7 +1344,7 @@ impl fmt::Display for UpdateError {
                 write!(f, "invalid component for operation")
             }
             Self::InvalidPreferredSlotId => {
-                write!(f, "update to preferred boot SlotId is not permitted")
+                write!(f, "updating a bootloader preferred slot is not permitted")
             }
         }
     }

gateway-sp-comms/src/error.rs

@@ -116,7 +116,7 @@ pub enum UpdateError {
     InvalidComponent,
     #[error("an image was not found")]
     ImageNotFound,
-    #[error("cannot update preferred boot image")]
+    #[error("updating a bootloader preferred slot is not permitted")]
     InvalidPreferredSlotId,
 }