fix: incremental pca example patching logic (#2285)

Author: ethanglaser

examples/sklearnex/incremental_pca_dpctl.py

@@ -23,7 +23,8 @@
 # Import estimator via sklearnex's patch mechanism from sklearn
 from sklearnex import patch_sklearn, sklearn_is_patched
 
-patch_sklearn()
+# IncrementalPCA is currently in preview module, so extra flag is required
+patch_sklearn(preview=True)
 
 # Function that can validate current state of patching
 sklearn_is_patched()