Fix RSS subject placeholders in campaign notifications

[ashishpatel1992]

Description

For RSS campaigns, the RssFeedPlugin updates the effective subject during campaign processing, but processqueue.php was still sending notify_start and notify_end emails using the original message subject. As a result, placeholders such as [RSS:N] could appear unprocessed in notification emails.

Updated queue processing to refresh $msgdata['subject'] from the plugin-updatedmessage data after campaignStarted() and after processSendingCampaignFinished().

This keeps non-RSS behaviour unchanged and makes both campaign notificationemails use the final resolved subject.

Changes:

Started Campaign

Before

phpList has started sending the campaign with subject XXXXXX has [RSS:N] new posts

to view the progress of this campaign, go to https://example.com/lists/admin/?page=messages&tab=active 

After

phpList has started sending the campaign with subject XXXXXX has 5 new posts

to view the progress of this campaign, go to https://example.com/lists/admin/?page=messages&tab=active 

Finishing Campaign

Before

phpList has finished sending the campaign with subject XXXXXX has [RSS:N] new posts

to view the statistics of this campaign, go to https://example.com/lists/admin/?page=statsoverview&id=10

After

phpList has finished sending the campaign with subject XXXXXX has 5 new posts

to view the statistics of this campaign, go to https://example.com/lists/admin/?page=statsoverview&id=10

Related Issue

Screenshots (if appropriate):