dashboard: align 'no notifications available' icon in notifications page

dashboard: align 'no notifications available' icon in notifications page

The icon displayed when there are no notifications available in the
notifications page was slightly misaligned with the message text.

This change adjusts the layout to properly align the icon with the
message using flexbox and removes unnecessary spacing.

Fixes: https://tracker.ceph.com/issues/74598
Signed-off-by: Shashiranjan Singh <singhshashiranjan34@gmail.com>
Signed-off-by: Shashiranjan singh <singhshashiranjan34@gmail.com>