Make clippy happy in Windows

src/self_update.rs

@@ -51,7 +51,7 @@ pub fn self_update() -> Result<(), Error> {
                     .spawn()
                     .and_then(|mut c| c.wait())
                     .context(ErrorKind::SelfUpdate)?;
-                Err(ErrorKind::Upgraded(status))?
+                return Err(ErrorKind::Upgraded(status).into());
             }
         }
     }

src/steps/powershell.rs

@@ -60,7 +60,7 @@ impl Powershell {
         let powershell = require_option(self.path.as_ref())?;
 
         if !Self::has_module(&powershell, "PSWindowsUpdate") {
-            Err(ErrorKind::SkipStep)?;
+            return Err(ErrorKind::SkipStep.into());
         }
         print_separator("Windows Update");