[simd.creation] Use return type from synopsis

The return type in the itemdecl/-descr was obviously wrong (ABI tag as
first template argument to the simd_mask alias template and missing
closing template bracket). The synopsis had the correct return type.

Author: mattkretz

source/numerics.tex

@@ -17978,8 +17978,8 @@
   constexpr simd<T, (basic_simd<T, Abis>::size() + ...)>
     simd_cat(const basic_simd<T, Abis>&... xs) noexcept;
 template<size_t Bytes, class... Abis>
-  constexpr simd_mask<@\exposid{deduce-abi-t}@<@\exposid{integer-from}@<Bytes>,
-      (basic_simd_mask<Bytes, Abis>::size() + ...)>
+  constexpr basic_simd_mask<Bytes, @\exposid{deduce-abi-t}@<@\exposid{integer-from}@<Bytes>,
+                            (basic_simd_mask<Bytes, Abis>::size() + ...)>>
     simd_cat(const basic_simd_mask<Bytes, Abis>&... xs) noexcept;
 \end{itemdecl}
 
@@ -17992,8 +17992,9 @@
    is enabled.
  \item
    For the second overload
-   \tcode{simd_mask<\exposid{deduce-abi-t}<\exposid{integer-from}<Bytes>,
-   (basic_simd_mask\brk{}<\brk{}Bytes, Abis>::size() + ...)>} is enabled.
+   \tcode{basic_simd_mask<Bytes,
+   \exposid{deduce-abi-t}<\exposid{integer-from}<Bytes>,
+   (ba\-sic_simd_mask<Bytes, Abis>::size() + ...)>>} is enabled.
 \end{itemize}
 
 \pnum