Remove speedreader updater component (enabling theme support)

[antonok-edm]

The Brave Speedreader Updater component (jicbkmdloagakknpihibphagfckhjdih) only ships two data files in its CRX - content-stylesheet.css and speedreader-updater.dat.

The .dat file is completely unused, since Speedreader has been updated to no longer use the adblock list-based backend.

content-stylesheet.css is still used to override the style in brave-core, but it does so unconditionally even though there is already a speedreader stylesheet bundled inside brave-core. The stylesheet is now stable enough to not need to be updated dynamically, so it should be safe to remove this as well.

The stylesheet currently shipped by the component updater is fairly old and there is a PR (brave-experiments/SpeedReader#36) to update it to match the current version in brave-core, enabling theme support. Merging this will make themes work without requiring the component at all.

Once this has enough roll-out, we should remove the speedreader component from brave-core-crx-packager as well.

[MadhaviSeelam]

Verification PASSED using

Brave | 1.45.78 Chromium: 106.0.5249.65 (Official Build) beta (64-bit)
-- | --
Revision | 3269dc3633cdd2ab94546fdbe54962e45b17a6e0-refs/branch-heads/5249@{#580}
OS | Windows 11 Version 21H2 (Build 22000.978)

1. Install 1.45.78
2. launch Brave
3. verified jicbkmdloagakknpihibphagfckhjdih is no longer available in the component directory
4. opened brave://settings/appearance and selected Light
5. visited https://www.bbc.com/travel/article/20220928-mexicos-ancient-unknown-pyramids
6. clicked on the Speedreader icon
7. verified the Light theme was applied in Speedreader mode to the article
8. switch to Dark theme in brave://settings/appearance
9. return to the article tab
10. verified the Dark theme was applied in Speedreader mode to the article
11. open brave://components

Confirmed Brave SpeedReader Updater component is no longer available

step 3	step 4	step7	step8	step10	step 11

[stephendonner]

Verification PASSED using

Brave	1.46.29 Chromium: 106.0.5249.91 (Official Build) nightly (x86_64)
Revision	fa96d5f07b1177d1bf5009f647a5b8c629762157-refs/branch-heads/5249@{#707}
OS	macOS Version 11.7 (Build 20G817)

Steps:

1. installed 1.45.84
2. launched Brave
3. verified jicbkmdloagakknpihibphagfckhjdih is no longer available in the component directory
4. opened brave://settings/appearance and selected Light
5. visited https://www.bbc.com/travel/article/20220928-mexicos-ancient-unknown-pyramids
6. clicked on the Speedreader icon
7. verified the Light theme was applied in Speedreader mode to the article
8. switch to Dark theme in brave://settings/appearance
9. returned to the article tab
10. verified the Dark theme was applied in Speedreader mode to the article
11. opened brave://components

Confirmed Brave SpeedReader Updater component is no longer available

step 3	step 4	step 7	step 8	step 10	step 11

[LaurenWags]

Verified on Google Pixel 3 XL with Android 12 running 1.45.100.

Speedreader is not available on Android yet (#22968) however, confirmed that chrome://components does not show Speedreader component:

[btlechowski]

Verification passed on

Brave	1.45.90 Chromium: 106.0.5249.103 (Official Build) beta (64-bit)
Revision	182570408a1f25ab2731ef5f283b918df9b9f956-refs/branch-heads/5249_91@{#6}
OS	Ubuntu 18.04 LTS

Steps:

1. installed 1.45.x
2. launched Brave
3. verified jicbkmdloagakknpihibphagfckhjdih is no longer available in the component directory
4. opened brave://settings/appearance and selected Light
5. visited https://www.bbc.com/travel/article/20220928-mexicos-ancient-unknown-pyramids
6. clicked on the Speedreader icon
7. verified the Light theme was applied in Speedreader mode to the article
8. switch to Dark theme in brave://settings/appearance
9. returned to the article tab
10. verified the Dark theme was applied in Speedreader mode to the article
11. opened brave://components

Confirmed Brave SpeedReader Updater component is no longer available

step 3	step 4	step 7	step 8	step 10	step 11