Use std::unordered_set::find instead of std::unordered_set::contains

Summary:
changelog: [internal]

I'm looking into JS exceptions in React 18 on Android and I've noticed we use [std::unordered_set::contains]((https://en.cppreference.com/w/cpp/container/unordered_set/contains) that is only supported in C++20. I don't think this causes the exceptions but I would like to eliminate this option.

Reviewed By: javache

Differential Revision: D34547741

fbshipit-source-id: 6cffcff3366e7579a2c0e19bc01ffcb355b9ddb6

ReactAndroid/src/main/java/com/facebook/react/fabric/jni/FabricMountingManager.cpp

@@ -403,7 +403,8 @@ void FabricMountingManager::executeMount(
             bool revisionCheck =
                 noRevisionCheck || newChildShadowView.props->revision > 1;
             bool allocationCheck =
-                !allocatedViewTags.contains(newChildShadowView.tag);
+                allocatedViewTags.find(newChildShadowView.tag) ==
+                allocatedViewTags.end();
             bool shouldCreateView =
                 shouldRememberAllocatedViews_ ? allocationCheck : revisionCheck;
             if (shouldCreateView) {
@@ -822,7 +823,7 @@ void FabricMountingManager::preallocateShadowView(
       return;
     }
     auto &allocatedViews = allocatedViewsIterator->second;
-    if (allocatedViews.contains(shadowView.tag)) {
+    if (allocatedViews.find(shadowView.tag) != allocatedViews.end()) {
       return;
     }
     allocatedViews.insert(shadowView.tag);