style: adjust font weight for breaking news prefix

- Change font weight from FontWeight.w600 to FontWeight.w500 for the breaking news prefix in headline tiles
- Update applied to three different headline tile widgets: HeadlineTileImageStart, HeadlineTileImageTop, and HeadlineTileTextOnly

Author: fulleni

lib/shared/widgets/feed_core/headline_tile_image_start.dart

@@ -97,7 +97,7 @@ class HeadlineTileImageStart extends StatelessWidget {
                             TextSpan(
                               text: '${l10n.breakingNewsPrefix} - ',
                               style: textTheme.titleMedium?.copyWith(
-                                fontWeight: FontWeight.w600,
+                                fontWeight: FontWeight.w500,
                                 color: colorScheme.primary,
                               ),
                             ),

lib/shared/widgets/feed_core/headline_tile_image_top.dart

@@ -115,7 +115,7 @@ class HeadlineTileImageTop extends StatelessWidget {
                             TextSpan(
                               text: '${l10n.breakingNewsPrefix} - ',
                               style: textTheme.titleMedium?.copyWith(
-                                fontWeight: FontWeight.w600,
+                                fontWeight: FontWeight.w500,
                                 color: colorScheme.primary,
                               ),
                             ),

lib/shared/widgets/feed_core/headline_tile_text_only.dart

@@ -70,7 +70,7 @@ class HeadlineTileTextOnly extends StatelessWidget {
                             TextSpan(
                               text: '${l10n.breakingNewsPrefix} - ',
                               style: textTheme.titleMedium?.copyWith(
-                                fontWeight: FontWeight.w600,
+                                fontWeight: FontWeight.w500,
                                 color: colorScheme.primary,
                               ),
                             ),