re-order atan2 in trig op heading

Author: tex3d

llvm/docs/GlobalISel/GenericOpcode.rst

@@ -633,7 +633,7 @@ G_FCEIL, G_FSQRT, G_FFLOOR, G_FRINT, G_FNEARBYINT
 
 These correspond to the standard C functions of the same name.
 
-G_FCOS, G_FSIN, G_FTAN, G_FACOS, G_FASIN, G_FATAN, G_FCOSH, G_FSINH, G_FTANH, G_FATAN2
+G_FCOS, G_FSIN, G_FTAN, G_FACOS, G_FASIN, G_FATAN, G_FATAN2, G_FCOSH, G_FSINH, G_FTANH
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 These correspond to the standard C trigonometry functions of the same name.