fix: remove mdformat-admon and custom no-escape plugin

[KyleKing]

Summary

Resolve mdformat issues raised while upgrading to mdformat-mkdocs in #15011

Test Plan

> uv run --no-project --isolated --with-requirements docs/requirements.txt scripts/generate_mkdocs.py
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.33s
     Running `target/debug/ruff_dev generate-docs`
Rule F401 references deprecated option lint.ignore-init-module-imports.
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.13s
     Running `target/debug/ruff_dev generate-rules-table`
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.13s
     Running `target/debug/ruff_dev generate-options`
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.13s
     Running `target/debug/ruff rule --all --output-format json`  

[github-actions]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

✅ ecosystem check detected no linter changes.

Formatter (stable)

✅ ecosystem check detected no format changes.

Formatter (preview)

✅ ecosystem check detected no format changes.

[dhruvmanila]

Thank you!