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 (if you happen to be generating them on a x86 machine), which gets checked in. See for example https://github.com/bitcoin/bitcoin/commit/1bc9988993ee84bc814e5a7f33cc90f670a19f6a#diff-e4b84be382c8ea33b83203ceb8c85296