Revert "Add trace points for class loading."

This reverts commit 88b9d89098a2556f39a104ffe389f38d2ecfc3a6.

Reason for revert: Regression on crystalball.

Change-Id: I2b8a2b30043e9e4e630b56ecce001fec205e8757
diff --git a/runtime/class_linker.cc b/runtime/class_linker.cc
index 682f358..124eb2b 100644
--- a/runtime/class_linker.cc
+++ b/runtime/class_linker.cc
@@ -3351,7 +3351,6 @@
                                                Handle<mirror::ClassLoader> class_loader,
                                                const DexFile& dex_file,
                                                const dex::ClassDef& dex_class_def) {
-  ScopedTrace trace([&]() { return android::base::StringPrintf("Defining %s", descriptor); });
   ScopedDefiningClass sdc(self);
   StackHandleScope<3> hs(self);
   metrics::AutoTimer timer{GetMetrics()->ClassLoadingTotalTime()};