test: add edge case tests for non-array error-codes (#615)

Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>
Co-authored-by: rowan-m <108052+rowan-m@users.noreply.github.com>

Author: rowan-m

tests/ReCaptcha/ResponseTest.php

@@ -112,7 +112,15 @@ public static function provideJson(): array
                 false, [ReCaptcha::E_INVALID_JSON], null, null, null, null, null,
             ],
             [
-                '{"success": false, "error-codes": "bad-request"}',
+                '{"success": false, "error-codes": "invalid-input-secret"}',
+                false, [ReCaptcha::E_UNKNOWN_ERROR], null, null, null, null, null,
+            ],
+            [
+                '{"success": false, "error-codes": null}',
+                false, [ReCaptcha::E_UNKNOWN_ERROR], null, null, null, null, null,
+            ],
+            [
+                '{"success": false, "error-codes": 123}',
                 false, [ReCaptcha::E_UNKNOWN_ERROR], null, null, null, null, null,
             ],
         ];