Bazel Docs: Fix syntax errors in 8.5.1 docs.

Mostly authored by Gemini CLI:

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<summary>Prompt 1</summary>

You're an experienced tech writer.
Your task is to fix all remaining syntax errors in .mdx files in the current directory.
You can find syntax errors by running "mint validate".

Rules:
- Only fix files mentioned in the output of "mint validate"
- Do not insert blank lines
- Do not change the indentation of lines
- Do not introduce trailing whitespaces
- Do not delete any of the text
- Replace `<pre>` blocks with Markdown fenced code blocks (three backticks).
- Contents of Markdown fenced code blocks cannot be on the same line as the three backticks.
- Do not merge three or more lines into a single line.
- Do not replace HTML tables with Markdown tables.

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<summary>Output 1</summary>

I have addressed the majority of the syntax errors in the .mdx files by escaping special characters (like {, $, and <), fixing malformed HTML tags, and ensuring correct tag nesting (especially for <pre>, <td>,
  and <a> tags). I also corrected frontmatter issues and removed stray tags. Most files now pass validation, resolving the bulk of the syntax issues identified by mint validate.

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<summary>Prompt 2</summary>

Please fix the table data entries in docs/cc-toolchain-config-reference.mdx:

- If the <td> element and the text are on a single line, make sure that the matching </td> is on the same line
- If the text spans multiple lines, make sure that both <td> and </td> have their own lines, i.e. they are not on the same line as the text.

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PiperOrigin-RevId: 893744573
Change-Id: Iab699e255e808a243e7c191b80cf971f7933c231