Update instructions.rst

According to other places in docs and my research on dumped wat files, I consider that funcidx for this call places on stack, not as parameter.

document/core/syntax/instructions.rst

@@ -764,7 +764,7 @@ Instructions in this group affect the flow of control.
      \CALLREF~\typeidx \\&&|&
      \CALLINDIRECT~\tableidx~\typeidx \\&&|&
      \RETURNCALL~\funcidx \\&&|&
-     \RETURNCALLREF~\funcidx \\&&|&
+     \RETURNCALLREF~\typeidx \\&&|&
      \RETURNCALLINDIRECT~\tableidx~\typeidx \\
    \end{array}