Undo hack to test dask shape

Author: crusaderky

src/array_api_extra/_lib/_funcs.py

@@ -556,7 +556,7 @@ def nunique(x: Array, /, *, xp: ModuleType | None = None) -> Array:
     _, counts = xp.unique_counts(x)
     n = _compat.size(counts)
     # FIXME https://github.com/data-apis/array-api-compat/pull/231
-    if n is None or math.isnan(n):  # e.g. Dask, ndonnx
+    if n is None:  # e.g. Dask, ndonnx
         return xp.astype(counts, xp.bool).sum()
     return xp.asarray(n, device=_compat.device(x))