[libc][test] Remove unused nan variables (#155894)

These are redefined/shadowed by the `if constexpr (FPBits::FRACTION_LEN
- 1 >= 5)` case below.

Added by #155569

Author: rupprecht

libc/test/src/math/smoke/TotalOrderTest.h

@@ -104,12 +104,6 @@ class TotalOrderTestTemplate : public LIBC_NAMESPACE::testing::FEnvSafeTest {
   }
 
   void testNaNPayloads(TotalOrderFunc func) {
-
-    T qnan_0x15 = FPBits::quiet_nan(Sign::POS, 0x15).get_val();
-    T neg_qnan_0x15 = FPBits::quiet_nan(Sign::NEG, 0x15).get_val();
-    T snan_0x15 = FPBits::signaling_nan(Sign::POS, 0x15).get_val();
-    T neg_snan_0x15 = FPBits::signaling_nan(Sign::NEG, 0x15).get_val();
-
     EXPECT_TRUE(funcWrapper(func, aNaN, aNaN));
     EXPECT_TRUE(funcWrapper(func, sNaN, sNaN));