Auto merge of #11697 - mrmiywj:form-index-getter, r=Ms2ger

indexed getter of form elements

<!-- Please describe your changes on the following line: -->

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #11405 (github issue number if applicable).

<!-- Either: -->
- [X] There are tests for these changes OR
- [ ] These changes do not require tests because _____

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="35" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/11697)
<!-- Reviewable:end -->

tests/wpt/metadata/MANIFEST.json

@@ -36064,6 +36064,12 @@
             "url": "/html/semantics/embedded-content/the-iframe-element/same_origin_parentage.html"
           }
         ],
+        "html/semantics/forms/the-form-element/form-indexed-element.html": [
+          {
+            "path": "html/semantics/forms/the-form-element/form-indexed-element.html",
+            "url": "/html/semantics/forms/the-form-element/form-indexed-element.html"
+          }
+        ],
         "url/url-domainToUnicode.html": [
           {
             "path": "url/url-domainToUnicode.html",

tests/wpt/metadata/old-tests/submission/Opera/script_scheduling/031.html.ini

@@ -1,5 +0,0 @@
-[031.html]
-  type: testharness
-  [ scheduler: focus and blur events]
-    expected: FAIL
-