index: fix notcurses_metric reference

doc/man/index.html

@@ -44,7 +44,7 @@
   <a href="notcurses_input.3.html">notcurses_input</a>—collecting input<br/>
   <a href="notcurses_lines.3.html">notcurses_lines</a>—drawing lines and boxes on <tt>ncplane</tt>s<br/>
   <a href="notcurses_menu.3.html">notcurses_menu</a>—menus on the top or bottom rows<br/>
-  <a href="notcurses_metric.3.html">notcurses_menu</a>—fixed-width formatting with metric suffixes<br/>
+  <a href="notcurses_metric.3.html">notcurses_metric</a>—fixed-width formatting with metric suffixes<br/>
   <a href="notcurses_multiselector.3.html">notcurses_multiselector</a>—high-level widget for selecting items from a set<br/>
   <a href="notcurses_reel.3.html">notcurses_reel</a>—high-level widget for hierarchical data<br/>
   <a href="notcurses_output.3.html">notcurses_output</a>—drawing text on <tt>ncplane</tt>s<br/>