Fix: Use pinentry-mac as pinentry binary on macOS for approvals

[Oisann]

I couldn't approve SSH Agent requests on macOS, it would just automatically deny any request.
This seems to be fixing the issue.

[Oisann]

I didn't really look into it yet, but I also had issues building locally. I get a binary that just dies, but the same commit produced a working binary using Github Actions on my fork (macOS arm64). Am I missing something obvious?

[quexten]

Any errors when it dies?

[quexten]

Either way, changes look good, thank you!

[Oisann]

Any errors when it dies?

jonas@Jonas-MBP-M2 ~/Development/goldwarden (oisann/macos-ssh-agent-pinentry-fix) % go build -v .
github.com/quexten/goldwarden/cli/agent/systemauth/pinentry
github.com/quexten/goldwarden
jonas@Jonas-MBP-M2 ~/Development/goldwarden (oisann/macos-ssh-agent-pinentry-fix) % ls -lAh
total 26416
drwxr-xr-x@ 17 jonas  staff   544B Oct 31 09:31 .git
drwxr-xr-x@  5 jonas  staff   160B Oct 28 13:24 .github
-rw-r--r--@  1 jonas  staff   101B Oct 28 13:24 .gitignore
-rw-r--r--@  1 jonas  staff   1.0K Oct 28 13:24 LICENSE
-rw-r--r--@  1 jonas  staff   3.2K Oct 28 13:24 Readme.md
drwxr-xr-x@ 10 jonas  staff   320B Oct 28 13:24 cli
-rw-r--r--@  1 jonas  staff   2.4K Oct 28 13:24 go.mod
-rw-r--r--@  1 jonas  staff    12K Oct 28 13:24 go.sum
-rwxr-xr-x@  1 jonas  staff    13M Oct 31 09:31 goldwarden
drwxr-xr-x@ 12 jonas  staff   384B Oct 28 13:24 gui
-rw-r--r--@  1 jonas  staff   1.9K Oct 28 13:24 main.go
jonas@Jonas-MBP-M2 ~/Development/goldwarden (oisann/macos-ssh-agent-pinentry-fix) % ./goldwarden
zsh: killed     ./goldwarden
jonas@Jonas-MBP-M2 ~/Development/goldwarden (oisann/macos-ssh-agent-pinentry-fix) % echo $?
137