Fix failing Flux stdlib tests

[stuartcarnie]

What

Running the Go test suite returns the following failures:

--- FAIL: TestFluxEndToEnd (49.96s)
    --- FAIL: TestFluxEndToEnd/influxdata/influxdb/v1 (0.57s)
        --- FAIL: TestFluxEndToEnd/influxdata/influxdb/v1/measurement_tag_values (0.12s)
            end_to_end_test.go:248: found 1 tables that were not empty
    --- FAIL: TestFluxEndToEnd/testing/chronograf (0.45s)
        --- FAIL: TestFluxEndToEnd/testing/chronograf/aggregate_window_median (0.12s)
            end_to_end_test.go:225: field type conflict
            end_to_end_test.go:248: found 3 tables that were not empty
    --- FAIL: TestFluxEndToEnd/testing/influxql (1.02s)
        --- FAIL: TestFluxEndToEnd/testing/influxql/elapsed (0.13s)
            end_to_end_test.go:238: found 2 tables that were not empty
    --- FAIL: TestFluxEndToEnd/range_stop (0.08s)
        end_to_end_test.go:248: found 2 tables that were not empty
FAIL
FAIL	github.com/influxdata/influxdb/v2/query/stdlib/testing	53.890s

[stuartcarnie]

Closed #19569