Check test failures on oldrel-Windows

[IndrajeetPatil]

cf. https://cloud.r-project.org/web/checks/check_results_see.html

 ══ Failed tests ════════════════════════════════════════════════════════════════
    ── Error ('test-plot.dw_data_tabulate.R:3:3'): `plot.dw_data_tabulate()` works with single table ──
    Error in `xy.coords(x, y, xlabel, ylabel, log)`: 'x' is a list, but does not have components 'x' and 'y'
    Backtrace:
        ▆
     1. ├─testthat::expect_s3_class(plot(x), "gg") at test-plot.dw_data_tabulate.R:3:3
     2. │ └─testthat::quasi_label(enquo(object), arg = "object")
     3. │   └─rlang::eval_bare(expr, quo_get_env(quo))
     4. ├─base::plot(x)
     5. └─graphics::plot.default(x)
     6.   └─grDevices::xy.coords(x, y, xlabel, ylabel, log)
    ── Error ('test-plot.dw_data_tabulate.R:8:3'): `plot.dw_data_tabulate()` works with multiple tables ──
    Error in `xy.coords(x, y, xlabel, ylabel, log)`: 'x' is a list, but does not have components 'x' and 'y'
    Backtrace:
        ▆
     1. ├─testthat::expect_true(is.list(plot(x))) at test-plot.dw_data_tabulate.R:8:3
     2. │ └─testthat::quasi_label(enquo(object), label, arg = "object")
     3. │   └─rlang::eval_bare(expr, quo_get_env(quo))
     4. ├─base::plot(x)
     5. └─graphics::plot.default(x)
     6.   └─grDevices::xy.coords(x, y, xlabel, ylabel, log)

    [ FAIL 2 | WARN 1 | SKIP 13 | PASS 31 ]

[strengejacke]

I think this is due to renaming the class attribute: https://github.com/easystats/datawizard/pull/517#discussion_r1649620697