binmiscctl.8: Change the example to armv7

[andrew]

Summary

armv6 is in the process of being removed.

Sponsored by: Arm Ltd

[emaste]

I found these via grep -r armv6 and wondered if we should pick e.g. arm64 instead - but I didn't look further to see if there's other context that would be specific to 32-bit or 32-bit arm.