vfs: flaky test TestDiskHealthChecking_Filesystem_Close on windows

[nicktrav]

See: https://github.com/cockroachdb/pebble/runs/6529596928?check_suite_focus=true

2022-05-20T18:08:36.8319398Z === RUN   TestDiskHealthChecking_Filesystem_Close
2022-05-20T18:08:36.8319606Z     disk_health_test.go:310: 
2022-05-20T18:08:36.8319913Z         	Error Trace:	disk_health_test.go:310
2022-05-20T18:08:36.8320305Z         	Error:      	map[string]time.Duration{} does not contain "foo"
2022-05-20T18:08:36.8320658Z         	Test:       	TestDiskHealthChecking_Filesystem_Close

[nicktrav]

Another instance of this in https://github.com/cockroachdb/pebble/runs/6576024347?check_suite_focus=true

2022-05-24T15:03:01.8013573Z === RUN   TestDiskHealthChecking_Filesystem_Close
2022-05-24T15:03:01.8014113Z     disk_health_test.go:310: 
2022-05-24T15:03:01.8014526Z         	Error Trace:	disk_health_test.go:310
2022-05-24T15:03:01.8015252Z         	Error:      	map[string]time.Duration{"foo":36546400} does not contain "bar"
2022-05-24T15:03:01.8015772Z         	Test:       	TestDiskHealthChecking_Filesystem_Close

[nicktrav]

2022-06-28T02:50:07.8771519Z === RUN   TestDiskHealthChecking_Filesystem/remove-all
2022-06-28T02:50:07.8771716Z     assertion_compare.go:313: 
2022-06-28T02:50:07.8772018Z         	Error Trace:	disk_health_test.go:276
2022-06-28T02:50:07.8772277Z         	Error:      	"0" is not greater than "0"
2022-06-28T02:50:07.8772735Z         	Test:       	TestDiskHealthChecking_Filesystem/remove-all
2022-06-28T02:50:07.8772905Z         	Messages:   	[]

Going to close this one out in favor of #1718. Seems whatever the issue is, it affects at least two OSes.