*: uprgade gopsutil to v3.20.12

[wshwsh12]

What problem does this PR solve?

Issue Number: tidb master branch 75f7485 build failed in MacOS. same with pingcap/tiflow#1385

../../../.gvm/pkgsets/go1.15/global/pkg/mod/github.com/shirou/gopsutil@v2.20.6+incompatible/disk/disk_darwin.go:67:51: cannot use stat.Mntfromname[:] (type []byte) as type []int8 in argument to common.IntToString
../../../.gvm/pkgsets/go1.15/global/pkg/mod/github.com/shirou/gopsutil@v2.20.6+incompatible/disk/disk_darwin.go:68:49: cannot use stat.Mntonname[:] (type []byte) as type []int8 in argument to common.IntToString
../../../.gvm/pkgsets/go1.15/global/pkg/mod/github.com/shirou/gopsutil@v2.20.6+incompatible/disk/disk_darwin.go:69:50: cannot use stat.Fstypename[:] (type []byte) as type []int8 in argument to common.IntToString
../../../.gvm/pkgsets/go1.15/global/pkg/mod/github.com/shirou/gopsutil@v2.20.6+incompatible/disk/disk_darwin.go:85:43: cannot use stat.Fstypename[:] (type []byte) as type []int8 in argument to common.IntToString

Problem Summary:

What is changed and how it works?

Proposal: xxx

What's Changed:

How it Works:

Related changes

Check List

Tests

• Unit test
• Integration test

Side effects

• Performance regression
  • Consumes more CPU
  • Consumes more MEM
• Breaking backward compatibility

Release note

• No release note

[XuHuaiyu]

LGTM

[AndreMouche]

/merge

[wshwsh12]

/merge

[ti-srebot]

/run-all-tests