Revert "Dart SDK roll for 2018-10-23 (#23439)" (#23471)

This reverts commit 70cb1318f1a15fb23002f8d2af4e77f064ed74ed.
diff --git a/bin/internal/engine.version b/bin/internal/engine.version
index 5ef6298..5ad8958 100644
--- a/bin/internal/engine.version
+++ b/bin/internal/engine.version
@@ -1 +1 @@
-26e8840de5d6fe801378301dd36d54c92b25bd3b
+2586e941225726f0429b9e67f4d9b6ab404d7b1e