[cons.slice], [gslice.cons] remove undeclared/undocumented copy constructor signatures

Author: jwakely

source/numerics.tex

@@ -7929,7 +7929,6 @@
 \begin{itemdecl}
 slice();
 slice(size_t start, size_t length, size_t stride);
-slice(const slice&);
 \end{itemdecl}
 
 \begin{itemdescr}
@@ -8230,7 +8229,6 @@
 gslice();
 gslice(size_t start, const valarray<size_t>& lengths,
        const valarray<size_t>& strides);
-gslice(const gslice&);
 \end{itemdecl}
 
 \begin{itemdescr}