size: make output compatible with -P

Before this change the output of `rclone size -P` would get corrupted
by the progress printing.

This is fixed by using operations.SyncPrintf instead of fmt.Printf.

Fixes #7912

cmd/size/size.go

@@ -4,7 +4,6 @@ package size
 import (
 	"context"
 	"encoding/json"
-	"fmt"
 	"os"
 	"strconv"
 
@@ -73,13 +72,13 @@ of the size command.
 			count := strconv.FormatInt(results.Count, 10)
 			countSuffix := fs.CountSuffix(results.Count).String()
 			if count == countSuffix {
-				fmt.Printf("Total objects: %s\n", count)
+				operations.SyncPrintf("Total objects: %s\n", count)
 			} else {
-				fmt.Printf("Total objects: %s (%s)\n", countSuffix, count)
+				operations.SyncPrintf("Total objects: %s (%s)\n", countSuffix, count)
 			}
-			fmt.Printf("Total size: %s (%d Byte)\n", fs.SizeSuffix(results.Bytes).ByteUnit(), results.Bytes)
+			operations.SyncPrintf("Total size: %s (%d Byte)\n", fs.SizeSuffix(results.Bytes).ByteUnit(), results.Bytes)
 			if results.Sizeless > 0 {
-				fmt.Printf("Total objects with unknown size: %s (%d)\n", fs.CountSuffix(results.Sizeless), results.Sizeless)
+				operations.SyncPrintf("Total objects with unknown size: %s (%d)\n", fs.CountSuffix(results.Sizeless), results.Sizeless)
 			}
 			return nil
 		})