Fix expected failure assertion in S3EncryptionModesLiveTest

Ensure test fails if reading object does not throw an exception.

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
Signed-off-by: Stephen Cuppett <steve@cuppett.com>

Author: cuppett

tests/lib/Files/ObjectStore/S3EncryptionModesLiveTest.php

@@ -138,14 +138,15 @@ private function assertReadFails(S3 $s3, string $urn): void {
 				return true;
 			});
 			stream_get_contents($s3->readObject($urn));
-			$this->fail("Expected reading '$urn' to fail");
 		} catch (\Exception) {
 			foreach ($warnings as $warning) {
 				$this->assertStringStartsWith('fopen(', $warning);
 			}
+			return;
 		} finally {
 			restore_error_handler();
 		}
+		$this->fail("Expected reading '$urn' to fail");
 	}
 
 	// --- Per-mode matrix -----------------------------------------------------------------