Update ReleaseNotes.md

PRs: openvinotoolkit#3556 and openvinotoolkit#3583

Author: Nikita Savelyev

ReleaseNotes.md

@@ -9,7 +9,7 @@ Post-training Quantization:
 - General:
   - ...
 - Features:
-  - ...
+  - Introduced `group_size_fallback_mode` advanced weight compression parameter. This specifies how to handle nodes that do not support a default group size value. By default it is set to `GroupSizeFallbackMode.IGNORE`. This corresponds to skipping nodes that cannot be compressed with the given group size.
 - Fixes:
   - ...
 - Improvements: