runtime: TestReadMetrics failures

```
#!watchflakes
post <- pkg == "runtime" && test == "TestReadMetrics"
```

Issue created automatically to collect these failures.

Example ([log](https://build.golang.org/log/a125e825376957c19efca4d0c5dee5385b8d5a01)):

    --- FAIL: TestReadMetrics (0.00s)
        metrics_test.go:147: live bytes: 5894368 > heap alloc: 5882216


— [watchflakes](https://go.dev/wiki/Watchflakes)
