tests: Remove xfail for SQLFrame `Expr.skew` #12286

Job	Run time
plotly (3.12, ubuntu-latest)	1m 41s
scikit-lego (3.11, ubuntu-latest)	4m 5s
pointblank (3.12, ubuntu-latest)	6m 38s
hierarchicalforecast (3.12, ubuntu-latest)	23s
formulaic (3.12, ubuntu-latest)	59s
tubular (3.12, ubuntu-latest)	1m 58s
shiny (3.12, ubuntu-latest)	2m 42s
tea-tasting (3.12, ubuntu-latest)	24s
marimo (3.12, ubuntu-latest, core,optional)	2m 14s
altair (3.12, ubuntu-latest)	2m 19s
fairlearn (3.12, ubuntu-latest)	28s
validoopsie (3.9, ubuntu-latest)	2m 2s
gt-extras (3.12, ubuntu-latest)	26s
darts (3.12, ubuntu-latest)	40s
validoopsie (3.12, ubuntu-latest)	2m 2s
	29m 1s

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