iis: Relative paths on the VS project file

There are a ModSecurityIIS solution and project files, those
were using hard coded paths to meet the dependencies. As
consequence of the last update in our build scripts, now we
are able to built the dependencies and load it to our Visual
Studio project using relative paths.
iss: Removes Post-Build event.

There was a copy on Post-Build event using a hard coded path.
This patch removes this Post-Build event.