[libc][obvious] fix formatting mistake

[michaelrj]

Summary

I missed two instances of "SetUp" being replaced by "set_up" and
"TearDown" being replaced by "tear_down" when finalizing the formatting
change. This fixes that.

libc/benchmarks/LibcBenchmarkTest.cpp

if (!MaybeTimepoints)
       return {};
     assert(!MaybeTimepoints->empty());
     const Duration timepoint = MaybeTimepoints->front();
     MaybeTimepoints->pop();
     return timepoint;
   }
 
 protected:
-  void set_up() override { Options.Log = BenchmarkLog::Full; }
+  void SetUp() override { Options.Log = BenchmarkLog::Full; }
 
-  void tear_down() override {
+  void TearDown() override {
     // We make sure all the expected measurements were performed.
     if (MaybeTimepoints)
       EXPECT_THAT(*MaybeTimepoints, IsEmpty());
   }
 
   BenchmarkResult run() {
     return benchmark(Options, ParameterProvider, DummyFunction, *this);
   }

libc/test/src/signal/sigprocmask_test.cpp

 
 #include "test/ErrnoSetterMatcher.h"
 #include "utils/UnitTest/Test.h"
 
 class LlvmLibcSignalTest : public __llvm_libc::testing::Test {
   sigset_t oldSet;
 
 public:
-  void set_up() override { __llvm_libc::sigprocmask(0, nullptr, &oldSet); }
+  void SetUp() override { __llvm_libc::sigprocmask(0, nullptr, &oldSet); }
 
-  void tear_down() override {
+  void TearDown() override {
     __llvm_libc::sigprocmask(SIG_SETMASK, &oldSet, nullptr);
   }
 };
 
 using __llvm_libc::testing::ErrnoSetterMatcher::Fails;
 using __llvm_libc::testing::ErrnoSetterMatcher::Succeeds;
 
 // This tests for invalid input.