apply code suggestion

Co-authored-by: John Paul E. Balandan, CPA <[email protected]>

Author: michalsn

system/HTTP/SSEResponse.php

@@ -125,7 +125,7 @@ private function formatMultiline(string $prefix, string $value): string
         $output = '';
 
         foreach (explode("\n", $value) as $line) {
-            $output .= ($prefix !== '' ? "{$prefix}: " : ': ') . $line . "\n";
+            $output .= "{$prefix}: " . $line . "\n";
         }
 
         return $output . "\n";