Fix this unit test now with ggplot2 v4.0.0 in mind

See https://www.tidyverse.org/blog/2025/09/ggplot2-4-0-0/ for details about ggplot2's update

```R
 > class(vis_gene(spe, geneid = c("sum_umi", rownames(spe)[1])))
[1] "ggplot2::ggplot" "ggplot"          "ggplot2::gg"     "S7_object"       "gg"
```

Author: lcolladotor

tests/testthat/test-vis_gene.R

@@ -47,9 +47,12 @@ test_that(
         )
 
         #   Trivially check success with legitimate input
-        expect_equal(
-            class(vis_gene(spe, geneid = c("sum_umi", rownames(spe)[1]))),
-            c("gg", "ggplot")
+        expect_true(
+            all(
+                c("gg", "ggplot") %in% class(
+                    vis_gene(spe, geneid = c("sum_umi", rownames(spe)[1]))
+                )
+            )
         )