title: What happens if I remove the auto added supportedRuntime element?
body: <p>I have my project target 4.0.
  I updated it to 4.5 and VS added</p>
  
  <pre><code>&lt;startup&gt;
      &lt;supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5"/&gt;
  &lt;/startup&gt;
  </code></pre>
  
  <p>On top of changing TargetFrameworkVersion and I am curious if this is redundant.
  My understanding is that if runtime doesn't find supportedRuntime, it uses the .net version used to build exe. So in this case, the exe is built using 4.5 and it also has  saying to use 4.5. Would it behave differently whether i have this  or not and run it on a machine that only has 4.0?</p>