Flaky test: TestReadWindowAggregateSource

failure in CI:

```
goroutine 472 [running]:
runtime/debug.Stack(0xc000bae180, 0x2669ba0, 0xc0009668c0)
/usr/local/go/src/runtime/debug/stack.go:24 +0x9d
runtime/debug.PrintStack()
/usr/local/go/src/runtime/debug/stack.go:16 +0x22
github.com/influxdata/flux/execute/executetest.RunSourceHelper.func1(0xc000f42500)
/go/pkg/mod/github.com/influxdata/flux@v0.66.1/execute/executetest/source.go:210 +0x57
panic(0x15ea960, 0xc000bae1b0)
/usr/local/go/src/runtime/panic.go:679 +0x1b2
github.com/influxdata/influxdb/v2/query/stdlib/influxdata/influxdb.createReadWindowAggregateSource(0x2658ee0, 0xc0000bad00, 0x7e4377a3fef1c2e0, 0xb76360f5884e188d, 0x2676960, 0xc0009668e0, 0x0, 0x0, 0x0, 0x0)
/go/src/github.com/influxdata/influxdb/query/stdlib/influxdata/influxdb/source.go:335 +0x2c5
github.com/influxdata/influxdb/v2/query/stdlib/influxdata/influxdb.CreateReadWindowAggregateSource(...)
/go/src/github.com/influxdata/influxdb/query/stdlib/influxdata/influxdb/source_internal_test.go:9
github.com/influxdata/influxdb/v2/query/stdlib/influxdata/influxdb_test.TestReadWindowAggregateSource.func1(0x7e4377a3fef1c2e0, 0xb76360f5884e188d, 0x203000, 0x0)
/go/src/github.com/influxdata/influxdb/query/stdlib/influxdata/influxdb/source_test.go:279 +0x40d
github.com/influxdata/flux/execute/executetest.RunSourceHelper(0xc000f42500, 0xc0009969d0, 0x2, 0x2, 0x0, 0x0, 0xc0000baf40)
/go/pkg/mod/github.com/influxdata/flux@v0.66.1/execute/executetest/source.go:216 +0xf7
github.com/influxdata/influxdb/v2/query/stdlib/influxdata/influxdb_test.TestReadWindowAggregateSource(0xc000f42500)
/go/src/github.com/influxdata/influxdb/query/stdlib/influxdata/influxdb/source_test.go:162 +0x679
testing.tRunner(0xc000f42500, 0x24bfc48)
/usr/local/go/src/testing/testing.go:909 +0xc9
created by testing.(*T).Run
/usr/local/go/src/testing/testing.go:960 +0x350
--- FAIL: TestReadWindowAggregateSource (0.00s)
source.go:211: caught panic: interface conversion: *mock.WindowAggregateStoreReader is not influxdb.WindowAggregateReader: missing method HasWindowAggregateCapability
FAIL
FAIL github.com/influxdata/influxdb/v2/query/stdlib/influxdata/influxdb 5.706s
```

this test was skipped here:
https://github.com/influxdata/influxdb/pull/17843/commits/6c24b671e59e7d99b6057ef30d8806f7446ab11e