style(content_management): decrease column spacing in headlines page

- Change column spacing from AppSpacing.md to AppSpacing.sm in the DataTable widget

Author: fulleni

lib/content_management/view/headlines_page.dart

@@ -175,7 +175,7 @@ class _HeadlinesPageState extends State<HeadlinesPage> {
                       fit: FlexFit.tight,
                       headingRowHeight: 56,
                       dataRowHeight: 56,
-                      columnSpacing: AppSpacing.md,
+                      columnSpacing: AppSpacing.sm,
                       horizontalMargin: AppSpacing.md,
                     );
                   },