Fix several ESLint violations in chrome/test/data/webui/chromeos/

This is an effort to re-enable ESLint for this folder. Previously this
folder had custom ESLint rules, then ESLint checks were completely
turned off as part of eliminating custom ESLint rules.

In this patch fixing 600+ violations that can be fixed automatically
with ESLint's --fix flag, running the command below.

third_party/node/linux/node-linux-x64/bin/node \
    third_party/node/node_modules/eslint/bin/eslint \
    --config tools/web_dev_style/eslint.config.mjs \
    `find chrome/test/data/webui/chromeos/ -name '*.ts'` --fix

followed by
git cl -format --js chrome/test/data/webui/chromeos/

Bug: 369766161
Change-Id: I33fd6a11cf954f6a656bf22227015256845e3c75
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6194293
Auto-Submit: Demetrios Papadopoulos <dpapad@chromium.org>
Commit-Queue: Kyle Horimoto <khorimoto@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1410555}