Update gopsutil to support darwin/arm64

[radeksimko]

The old version of gopsutil doesn't seem to support Apple Silicon (darwin/arm64), causing debugcharts to fail to compile entirely on that platform:

go: downloading github.com/gorilla/handlers v1.4.2
go: downloading golang.org/x/sys v0.0.0-20191220220014-0732a990476f
# github.com/shirou/gopsutil/cpu
../../../../pkg/mod/github.com/shirou/gopsutil@v2.19.11+incompatible/cpu/cpu_darwin_cgo.go:13:5: warning: 'TARGET_OS_MAC' is not defined, evaluates to 0 [-Wundef-prefix=TARGET_OS_]
# github.com/shirou/gopsutil/process
../../../../pkg/mod/github.com/shirou/gopsutil@v2.19.11+incompatible/process/process_darwin.go:559:34: undefined: KinfoProc
../../../../pkg/mod/github.com/shirou/gopsutil@v2.19.11+incompatible/process/process_darwin.go:560:8: undefined: KinfoProc
../../../../pkg/mod/github.com/shirou/gopsutil@v2.19.11+incompatible/process/process_darwin.go:573:32: undefined: KinfoProc
../../../../pkg/mod/github.com/shirou/gopsutil@v2.19.11+incompatible/process/process_darwin.go:577:62: undefined: KinfoProc

I am therefore proposing to update that dependency, which seems to have resolved the problem for me.

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Thank you for this great project!