askrene: round capacity *down* when converting to fp16.

Conversion is lossy, and we don't want to spend more than the channel,
so it's conservative to round down here.

This doesn't actually help our test though!

Signed-off-by: Rusty Russell <[email protected]>

plugins/askrene/askrene.c

@@ -169,8 +169,9 @@ static fp16_t *get_capacities(const tal_t *ctx,
 				   "get_capacity failed for channel?");
 			cap = AMOUNT_SAT(0);
 		}
+		/* Pessimistic: round down! */
 		caps[gossmap_chan_idx(gossmap, c)]
-			= u64_to_fp16(cap.satoshis, true); /* Raw: fp16 */
+			= u64_to_fp16(cap.satoshis, false); /* Raw: fp16 */
 	}
 	return caps;
 }