[simd.syn] Remove duplicate using simd::abs; (#8163)

Author: Rageking8

source/numerics.tex

@@ -17074,7 +17074,6 @@
   using simd::scalbln;
   using simd::cbrt;
   using simd::abs;
-  using simd::abs;
   using simd::fabs;
   using simd::hypot;
   using simd::pow;