Code Quality: Delete unused function from PHP Sync Issue generation s…

…cript (WordPress#68947)

Co-authored-by: t-hamano <wildworks@git.wordpress.org>
Co-authored-by: Mamaduka <mamaduka@git.wordpress.org>

bin/generate-php-sync-issue.mjs

@@ -156,17 +156,6 @@ async function main() {
 	fs.writeFileSync( nodePath.join( __dirname, 'issueContent.md' ), content );
 }
 
-/**
- * Checks if the first date is after the second date.
- *
- * @param {string} date1 - The first date.
- * @param {string} date2 - The second date.
- * @return {boolean} - Returns true if the first date is after the second date, false otherwise.
- */
-function isAfter( date1, date2 ) {
-	return new Date( date1 ) > new Date( date2 );
-}
-
 function validateDate( sinceArg ) {
 	const sinceDate = new Date( sinceArg );
 	const maxPreviousDate = new Date();