Disable cosmetic filtering on Speedreader pages

[ShivanKaul]

Description

Speedreader can interact badly with Shields and adblock lists: #38118. Also, Speedreader causes two scrollbars to appear on https://metro.co.uk/2023/01/01/manchester-man-ate-124-kebabs-in-month-for-charity-18023290/ because of EasyList Cookie because of the rule metro.co.uk##body,html:style(overflow: auto !important; position: initial !important;)

We should just disable Shields when Speedreader is active. The privacy risk is minimal given that in Speedreader mode the website is heavily bounded in what it can do.

Steps to reproduce

1. Ensure EasyList Cookie is enabled in brave://settings/shields/filters
2. Go to https://metro.co.uk/2023/01/01/manchester-man-ate-124-kebabs-in-month-for-charity-18023290/ and enable Screenreader

Actual result

1. Shields is enabled
2. Double scrollbar

Expected result

1. Shields should be disabled/unclickable (similar to how it is on internal pages)
2. No double scrollbar

Reproduces how often

Easily reproduced

Brave version (brave://version info)

1.70.52 Chromium: 127.0.6533.88 (Official Build) nightly (arm64)

Channel information

• release (stable)
• beta
• nightly

Reproducibility

• with Brave Shields disabled
• with Brave Rewards disabled
• in the latest version of Chrome

Miscellaneous information

No response

[MadhaviSeelam]

Verification PASSED using

Brave | 1.75.133 Chromium: 132.0.6834.57 (Official Build) nightly (64-bit)
-- | --
Revision | ce1787778a7a5d92e63a29f8be965494ef49cbbd
OS | Windows 11 Version 24H2 (Build 26100.2605)

Reproduced the issue using STR from the description in 1.73.104

Verified the issue using STR from the description in 1.73.104

• Confirmed EasyList Cookie is enabled in brave://settings/shields/filters
• Confirmed when Speedreader is enabled, Shields is disabled and unclickable
• Confirmed no double scrollbar is shown

example	example	example