[html] HTML breadcrumbs don't work right when optional end tags omitted

- VSCode Version: 1.42.0-insider - OS Version: Linux Mint 19.3 Steps to Reproduce: 1. Create an HTML document. Sprinkle liberally with `<p>`, `<li>` (inside of `<ul>` or `<ol>`, obviously), `<tr>` or `<td>` inside of `<table>`, and any other elements noted in the HTML5 spec as having optional end tags (see https://html.spec.whatwg.org/#syntax-tag-omission). 2. If you closed the various tags above with their end tags (e.g., `</p>`), then run the page through something like HTML Tidy (I am using v5.7.28), passing in the `--omit-optional-tags yes` argument. 3. Open the reformatted file in VSCode and navigate somewhere where there are multiple `<p>` or `<li>` or similar in a row. Note that there will be a breadcrumb for **each** open tag, because VSCode is apparently looking for end tags to close off the element, even though it is not required. In a complex document, this make VSCode breadcrumbs pretty worthless. Here is an example, before a Tidy reformat, with focus on the third list item element in the fourth paragraph (note breadcrumbs working as expected):  And here are the breadcrumbs after the Tidy reformat, with focus on the same list item element:  Does this issue occur when all extensions are disabled?: Yes