doc: Remove bitness from bitcoin-qt help message and manpage

Remove the `(64-bit)` from the bitcoin-qt help message.

Since removing the Windows 32-bit builds, it is no longer information
that is often useful for troubleshooting. This never worked for other
architectures than x86, and the only 32-bit x86 build left is the Linux
one. Linux users tend to know what architecture they are using.

It also accidentally ends up in the bitcoin-qt manpage.

Author: laanwj

src/qt/utilitydialog.cpp

@@ -34,14 +34,6 @@ HelpMessageDialog::HelpMessageDialog(interfaces::Node& node, QWidget *parent, bo
     ui->setupUi(this);
 
     QString version = QString{PACKAGE_NAME} + " " + tr("version") + " " + QString::fromStdString(FormatFullVersion());
-    /* On x86 add a bit specifier to the version so that users can distinguish between
-     * 32 and 64 bit builds. On other architectures, 32/64 bit may be more ambiguous.
-     */
-#if defined(__x86_64__)
-    version += " " + tr("(%1-bit)").arg(64);
-#elif defined(__i386__ )
-    version += " " + tr("(%1-bit)").arg(32);
-#endif
 
     if (about)
     {