fix some typo in struct name comments (#19513)

Signed-off-by: coderwander <770732124@qq.com>

cmd/api-router.go

@@ -64,7 +64,7 @@ func setObjectLayer(o ObjectLayer) {
 	globalObjLayerMutex.Unlock()
 }
 
-// objectAPIHandler implements and provides http handlers for S3 API.
+// objectAPIHandlers implements and provides http handlers for S3 API.
 type objectAPIHandlers struct {
 	ObjectAPI func() ObjectLayer
 }