Fix duplicate extraAnnouncements and improve patch detection

- Remove duplicate workbench.welcomePage.extraAnnouncements entry
- Add fix-eol-banner.patch duplicate detection to utils.sh
- Prevents duplicate patch application in CI

Author: Tajudeen

src/vs/workbench/contrib/welcomeGettingStarted/browser/gettingStarted.contribution.ts

@@ -308,12 +308,6 @@ configurationRegistry.registerConfiguration({
 			default: true,
 			description: localize('workbench.welcomePage.extraAnnouncements', "When enabled, the get started page loads additional announcements from !!APP_NAME!!'s repository.")
 		},
-		'workbench.welcomePage.extraAnnouncements': {
-			scope: ConfigurationScope.MACHINE,
-			type: 'boolean',
-			default: true,
-			description: localize('workbench.welcomePage.extraAnnouncements', "When enabled, the get started page loads additional announcements from !!APP_NAME!!'s repository.")
-		},
 		'workbench.startupEditor': {
 			'scope': ConfigurationScope.RESOURCE,
 			'type': 'string',