Mention the update to C-Blosc2 2.19.1

Author: FrancescAlted

RELEASE_NOTES.md

@@ -19,6 +19,8 @@ More complex slicing is now supported.
 * Minor bug fixes to ensure that Blosc2 indexing does not introduce dummy dimensions when NumPy does not,
 and a more comprehensive `squeeze` function which squeezes specified dimensions.
 
+* C-Blosc2 internal library updated to latest 2.19.1.
+
 ## Changes from 3.5.0 to 3.5.1
 
 * Reduced memory usage when computing slices of lazy expressions.