refactor(FileService): remove redundant docblock from private method

The method name extractValidSignRequestId() and its return type ?int
already express the full contract. The comment was paraphrasing both
without adding new information.

Signed-off-by: Vitor Mattos <1079143+vitormattos@users.noreply.github.com>

Author: vitormattos

lib/Service/FileService.php

@@ -664,21 +664,17 @@ private function mapSignerDetailsToSummary(array $signers): array {
 		return $summaries;
 	}
 
-	/**
-	 * Extracts and type-casts signRequestId from signer data.
-	 * Returns null if signRequestId is missing, null, non-numeric, or cannot be converted.
-	 */
 	private function extractValidSignRequestId(array $signerData): ?int {
 		$signRequestId = $signerData['signRequestId'] ?? null;
-		
+
 		if (is_int($signRequestId)) {
 			return $signRequestId;
 		}
-		
+
 		if (is_string($signRequestId) && ctype_digit($signRequestId)) {
 			return (int)$signRequestId;
 		}
-		
+
 		return null;
 	}