Fixed comment for pandas.unique (#39557) (#39643)

Co-authored-by: Vladimir Podolskiy <[email protected]>

Author: simonjayhawkins

pandas/core/algorithms.py

@@ -324,7 +324,8 @@ def unique(values):
     Hash table-based unique. Uniques are returned in order
     of appearance. This does NOT sort.
 
-    Significantly faster than numpy.unique. Includes NA values.
+    Significantly faster than numpy.unique for long enough sequences.
+    Includes NA values.
 
     Parameters
     ----------