Revert "Started looking for the dart plugin registrant at runtime  (#31418)" (#32162) (#32267)

This reverts commit e97c8016e398d91d414d298ae9ca87e735441476.

Co-authored-by: gaaclarke <30870216+gaaclarke@users.noreply.github.com>
diff --git a/runtime/dart_isolate.cc b/runtime/dart_isolate.cc
index bb62265..b6c5e41 100644
--- a/runtime/dart_isolate.cc
+++ b/runtime/dart_isolate.cc
@@ -706,9 +706,7 @@
                                ? tonic::ToDart(entrypoint.value().c_str())
                                : tonic::ToDart("main");
 
-  if (!FindAndInvokeDartPluginRegistrant()) {
-    InvokeDartPluginRegistrantIfAvailable(library_handle);
-  }
+  InvokeDartPluginRegistrantIfAvailable(library_handle);
 
   auto user_entrypoint_function =
       ::Dart_GetField(library_handle, entrypoint_handle);