[ios.init] Remove unused Init::init_cnt static member (#7263)

The text that made use of this variable was removed by LWG1123 and has
not been present in the WP since N3090. The effects of Init construction
and destruction are specified entirely without the use of this variable,
so it serves no purpose now.

Author: jwakely

source/iostreams.tex

@@ -1132,9 +1132,6 @@
     Init(const Init&) = default;
     ~Init();
     Init& operator=(const Init&) = default;
-
-  private:
-    static int init_cnt;        // \expos
   };
 }
 \end{codeblock}
@@ -1148,17 +1145,6 @@
 provided for by the functions declared in
 \libheaderref{cstdio}.
 
-\pnum
-For the sake of exposition, the maintained data is presented here as:
-\begin{itemize}
-\item
-\tcode{static int init_cnt},
-counts the number of
-constructor and destructor calls for class
-\tcode{Init},
-initialized to zero.
-\end{itemize}
-
 \indexlibraryctor{ios_base::Init}%
 \begin{itemdecl}
 Init();