[base] Drop obsolete Thread::YieldCPU.

test/cctest/test-threads.cc

Index: test/cctest/test-threads.cc
diff --git a/test/cctest/test-threads.cc b/test/cctest/test-threads.cc
index 0f332a3af7b0dfa2259a23e7c2326414fac617a0..e192bc155941d8f617bca42afa50b1cfb9ed90a7 100644
--- a/test/cctest/test-threads.cc
+++ b/test/cctest/test-threads.cc
@@ -70,7 +70,6 @@ class ThreadA : public v8::base::Thread {
     do {
       {
         v8::Unlocker unlocker(CcTest::isolate());
-        Thread::YieldCPU();
       }
     } while (turn != SECOND_TIME_FILL_CACHE);
 
@@ -102,8 +101,6 @@ class ThreadB : public v8::base::Thread {
           break;
         }
       }
-
-      Thread::YieldCPU();
     } while (true);
   }
 };