Use `with` in `macdeployqtplus` script.

contrib/macdeploy/macdeployqtplus

@@ -674,9 +674,8 @@ else:
 if verbose >= 2:
     print("+ Installing qt.conf +")
 
-f = open(os.path.join(applicationBundle.resourcesPath, "qt.conf"), "wb")
+with open(os.path.join(applicationBundle.resourcesPath, "qt.conf"), "wb") as f:
     f.write(qt_conf.encode())
-f.close()
 
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