wix: avoid an abort with 'hg help -k foo'

Previously:

 $ /c/Program\ Files/Mercurial/hg help -k merge-tools
 abort: No such file or directory: c:\Program Files\Mercurial\help\scripting.txt

The Inno installer seems OK, but the TortoiseHg required the same fix.  That got
queued with an additional change of 'helpFolder.guid' in guids.wxi (probably by
Steve).  I'm not sure if that is necessary here too.

contrib/wix/help.wxs

@@ -1,34 +1,35 b''
 <?xml version="1.0" encoding="utf-8"?>
 <Wix xmlns="http://schemas.microsoft.com/wix/2006/wi">
 
   <?include guids.wxi ?>
   <?include defines.wxi ?>
 
   <Fragment>
     <DirectoryRef Id="INSTALLDIR">
       <Directory Id="helpdir" Name="help" FileSource="$(var.SourceDir)">
         <Component Id="helpFolder" Guid="$(var.helpFolder.guid)" Win64='$(var.IsX64)'>
           <File Name="config.txt" KeyPath="yes" />
           <File Name="dates.txt" />
           <File Name="diffs.txt" />
           <File Name="environment.txt" />
           <File Name="extensions.txt" />
           <File Name="filesets.txt" />
           <File Name="glossary.txt" />
           <File Name="hgignore.txt" />
           <File Name="hgweb.txt" />
           <File Name="merge-tools.txt" />
           <File Name="multirevs.txt" />
           <File Name="patterns.txt" />
           <File Name="phases.txt" />
           <File Name="revisions.txt" />
           <File Name="revsets.txt" />
+          <File Name="scripting.txt" />
           <File Name="subrepos.txt" />
           <File Name="templates.txt" />
           <File Name="urls.txt" />
         </Component>
       </Directory>
     </DirectoryRef>
   </Fragment>
 
 </Wix>