Fix incompatibility of gopsutil dependency with macOS

What does this MR do and why?

Fix incompatibility of gopsutil dependency with macOS

We are seeing some compiler warnings when compiling workhorse on macOS

The actual bug is in the gopsutil package, which forgot to include the <TargetConditionals.h> header. This was fixed in gopsutil v3.21.3, but we are still pulling in v3.21.2.

Fix this bug by upgrading to the most recent bug release of the v3.21 release train, which is v3.21.12.

See also: gitaly!5570 (merged)

Screenshots or screen recordings

N/A

How to set up and validate locally

1. Check out branch
2. make clean && make should not raise any compiler warnings.

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