Replace "can not" with "cannot" in docs, user messages, and tests

src/qt/bitcoin.cpp

@@ -509,7 +509,7 @@ int GuiMain(int argc, char* argv[])
         InitError(strprintf(Untranslated("Error parsing command line arguments: %s\n"), error));
         // Create a message box, because the gui has neither been created nor has subscribed to core signals
         QMessageBox::critical(nullptr, PACKAGE_NAME,
-            // message can not be translated because translations have not been initialized
+            // message cannot be translated because translations have not been initialized
             QString::fromStdString("Error parsing command line arguments: %1.").arg(QString::fromStdString(error)));
         return EXIT_FAILURE;
     }