Merge bitcoin/bitcoin#24367: User-facing content and codebase doc fixups from transifex translator feedback

48742693ac Replace "can not" with "cannot" in docs, user messages, and tests (Jon Atack)
e670edd434 User-facing content fixups from transifex translator feedback (Jon Atack)

Pull request description:

  Closes #24366.

ACKs for top commit:
  laanwj:
    Code review re-ACK 48742693ac
  hebasto:
    re-ACK 48742693ac, only suggested change since my previous [review](https://github.com/bitcoin/bitcoin/pull/24367#pullrequestreview-885938219).

Tree-SHA512: 4dcdcb417251a413e65fab6070515e13a1267c8e0dbcf521386b842511391f24c84a0c2168fe13458c977682034466509bf2a3453719d4d94d3c568fd9f4adb4

src/qt/bitcoin.cpp

@@ -519,7 +519,7 @@ 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;
     }

src/qt/intro.cpp

@@ -298,7 +298,7 @@ void Intro::setStatus(int status, const QString &message, quint64 bytesAvailable
 
 void Intro::UpdateFreeSpaceLabel()
 {
-    QString freeString = tr("%1 GB of free space available").arg(m_bytes_available / GB_BYTES);
+    QString freeString = tr("%1 GB of space available").arg(m_bytes_available / GB_BYTES);
     if (m_bytes_available < m_required_space_gb * GB_BYTES) {
         freeString += " " + tr("(of %1 GB needed)").arg(m_required_space_gb);
         ui->freeSpace->setStyleSheet("QLabel { color: #800000 }");