LibC: Remove unused code from math.cpp

These are dead after 92c6ae57fc in #4622.

No behavior change.

Userland/Libraries/LibC/math.cpp

@@ -25,20 +25,6 @@
 #    pragma clang diagnostic ignored "-Wdouble-promotion"
 #endif
 
-template<size_t>
-constexpr double e_to_power();
-template<>
-constexpr double e_to_power<0>() { return 1; }
-template<size_t exponent>
-constexpr double e_to_power() { return M_E * e_to_power<exponent - 1>(); }
-
-template<size_t>
-constexpr size_t factorial();
-template<>
-constexpr size_t factorial<0>() { return 1; }
-template<size_t value>
-constexpr size_t factorial() { return value * factorial<value - 1>(); }
-
 template<size_t>
 constexpr size_t product_even();
 template<>