Update Blink GC plugin to reflect that Oilpan is now always enabled.

tools/clang/blink_gc_plugin/BlinkGCPluginOptions.h

Index: tools/clang/blink_gc_plugin/BlinkGCPluginOptions.h
diff --git a/tools/clang/blink_gc_plugin/BlinkGCPluginOptions.h b/tools/clang/blink_gc_plugin/BlinkGCPluginOptions.h
index 812d3a64eee17f869b6603d48eb8e3556dbd693d..52e648413929706ccf20a76db69bf6bd20fb8d80 100644
--- a/tools/clang/blink_gc_plugin/BlinkGCPluginOptions.h
+++ b/tools/clang/blink_gc_plugin/BlinkGCPluginOptions.h
@@ -11,11 +11,9 @@
 
 struct BlinkGCPluginOptions {
   BlinkGCPluginOptions()
-      : enable_oilpan(false),
-        dump_graph(false),
+      : dump_graph(false),
         warn_raw_ptr(false),
         warn_unneeded_finalizer(false) {}
-  bool enable_oilpan;
   bool dump_graph;
   bool warn_raw_ptr;
   bool warn_unneeded_finalizer;