tsan: remove unnecessary brackets

compiler-rt/lib/tsan/rtl/tsan_rtl.cpp

static void DoResetImpl(uptr epoch) {
   DPrintf("Resetting meta shadow...\n");
   ctx->metamap.ResetClocks();
   ctx->resetting = false;
 }
 
 // Clang does not understand locking all slots in the loop:
 // error: expecting mutex 'slot.mtx' to be held at start of each loop
 void DoReset(ThreadState* thr, uptr epoch) SANITIZER_NO_THREAD_SAFETY_ANALYSIS {
-  {
-    for (auto& slot : ctx->slots) {
-      slot.mtx.Lock();
-      if (UNLIKELY(epoch == 0))
-        epoch = ctx->global_epoch;
-      if (UNLIKELY(epoch != ctx->global_epoch)) {
-        // Epoch can't change once we've locked the first slot.
-        CHECK_EQ(slot.sid, 0);
-        slot.mtx.Unlock();
-        return;
-      }
-    }
-  }
   DPrintf("#%d: DoReset epoch=%lu\n", thr ? thr->tid : -1, epoch);
   DoResetImpl(epoch);
   for (auto& slot : ctx->slots) slot.mtx.Unlock();
 }
 
 void FlushShadowMemory() { DoReset(nullptr, 0); }
 
 static TidSlot* FindSlotAndLock(ThreadState* thr)