AST/Sema: Remove a couple of pointless FrontendStatsTracers

To get timings here, just use -fine-grained-timers.

Author: slavapestov

lib/AST/UnqualifiedLookup.cpp

@@ -240,9 +240,6 @@ void UnqualifiedLookupFactory::performUnqualifiedLookup() {
   auto localCounter = lookupCounter;
   (void)localCounter; // for debugging
 #endif
-  FrontendStatsTracer StatsTracer(Ctx.Stats,
-                                  "performUnqualifiedLookup",
-                                  DC->getParentSourceFile());
 
   if (options.contains(UnqualifiedLookupFlags::ModuleLookup)) {
     lookForAModuleWithTheGivenName(DC->getModuleScopeContext());

lib/Sema/CodeSynthesis.cpp

@@ -1693,11 +1693,6 @@ SynthesizeDefaultInitRequest::evaluate(Evaluator &evaluator,
                                        NominalTypeDecl *decl) const {
   auto &ctx = decl->getASTContext();
 
-  FrontendStatsTracer StatsTracer(ctx.Stats,
-                                  "define-default-ctor", decl);
-  PrettyStackTraceDecl stackTrace("defining default constructor for",
-                                  decl);
-
   // Create the default constructor.
   auto ctorKind = decl->isDistributedActor() ?
       ImplicitConstructorKind::DefaultDistributedActor :