Only treat updates to lazy as a new mount in legacy mode

Author: rickhanlonii

packages/react-reconciler/src/ReactFiberBeginWork.new.js

@@ -1635,7 +1635,7 @@ function mountIndeterminateComponent(
   Component,
   renderLanes,
 ) {
-  if (_current !== null) {
+  if (_current !== null && (workInProgress.mode & ConcurrentMode) === NoMode) {
     // An indeterminate component only mounts if it suspended inside a non-
     // concurrent tree, in an inconsistent state. We want to treat it like
     // a new mount, even though an empty version of it already committed.

packages/react-reconciler/src/ReactFiberBeginWork.old.js

@@ -1635,7 +1635,7 @@ function mountIndeterminateComponent(
   Component,
   renderLanes,
 ) {
-  if (_current !== null) {
+  if (_current !== null && (workInProgress.mode & ConcurrentMode) === NoMode) {
     // An indeterminate component only mounts if it suspended inside a non-
     // concurrent tree, in an inconsistent state. We want to treat it like
     // a new mount, even though an empty version of it already committed.