Don't check main frame requests through shields network delegate helper (uplift to 1.23.x)

[brave-builds]

Uplift of #8402
Resolves brave/brave-browser#15047

Pre-approval checklist:

• You have tested your change on Nightly.
• This contains text which needs to be translated.
  • There are more than 7 days before the release.
  • I've notified folks in #l10n on Slack that translations are needed.
• The PR milestones match the branch they are landing to.

Pre-merge checklist:

• You have checked CI and the builds, lint, and tests all pass or are not related to your PR.

Post-merge checklist:

• The associated issue milestone is set to the smallest version that the changes is landed on.

[kjozwiak]

post-init failed due to audit_deps as per https://ci.brave.com/job/pr-brave-browser-pr8402_no-more-blocked-by-extension_1.23.x-post-init/1/execution/node/144/log/. However, this is a known failure/warning that's unrelated to this specific PR.

test-browser failed on macOS as per https://ci.brave.com/job/pr-brave-browser-pr8402_no-more-blocked-by-extension_1.23.x-macos/1/execution/node/241/log/ & https://ci.brave.com/job/pr-brave-browser-pr8402_no-more-blocked-by-extension_1.23.x-macos/1/execution/node/244/log/. However, this these are known failures and unrelated to this specific PR.

16:56:15  5 tests crashed:
16:56:15      BraveStatsUpdaterBrowserTest.StatsUpdaterMigration (../../brave/browser/brave_stats/brave_stats_updater_browsertest.cc:275)
16:56:15      BraveStatsUpdaterBrowserTest.StatsUpdaterSetsFirstCheckPreference (../../brave/browser/brave_stats/brave_stats_updater_browsertest.cc:154)
16:56:15      BraveStatsUpdaterBrowserTest.StatsUpdaterStartupPingWithDefaultReferralCode (../../brave/browser/brave_stats/brave_stats_updater_browsertest.cc:229)
16:56:15      BraveStatsUpdaterBrowserTest.StatsUpdaterStartupPingWithReferralCode (../../brave/browser/brave_stats/brave_stats_updater_browsertest.cc:327)
16:56:15      BraveStatsUpdaterBrowserTest.StatsUpdaterThresholdSetsFirstCheckPreference (../../brave/browser/brave_stats/brave_stats_updater_browsertest.cc:191)

test-browser failed on Linux as per https://ci.brave.com/job/pr-brave-browser-pr8402_no-more-blocked-by-extension_1.23.x-linux/1/execution/node/241/log/ & https://ci.brave.com/job/pr-brave-browser-pr8402_no-more-blocked-by-extension_1.23.x-linux/1/execution/node/244/log/. However, this these are known failures and unrelated to this specific PR.

15:39:21  6 tests crashed:
15:39:21      BraveStatsUpdaterBrowserTest.StatsUpdaterMigration (../../brave/browser/brave_stats/brave_stats_updater_browsertest.cc:275)
15:39:21      BraveStatsUpdaterBrowserTest.StatsUpdaterSetsFirstCheckPreference (../../brave/browser/brave_stats/brave_stats_updater_browsertest.cc:154)
15:39:21      BraveStatsUpdaterBrowserTest.StatsUpdaterStartupPingWithDefaultReferralCode (../../brave/browser/brave_stats/brave_stats_updater_browsertest.cc:229)
15:39:21      BraveStatsUpdaterBrowserTest.StatsUpdaterStartupPingWithReferralCode (../../brave/browser/brave_stats/brave_stats_updater_browsertest.cc:327)
15:39:21      BraveStatsUpdaterBrowserTest.StatsUpdaterThresholdSetsFirstCheckPreference (../../brave/browser/brave_stats/brave_stats_updater_browsertest.cc:191)
15:39:21      RewardsPublisherBrowserTest.VisitRegisteredPublisher (../../brave/components/brave_rewards/browser/test/rewards_publisher_browsertest.cc:157)

[kjozwiak]

Uplift into 1.23.x approved after deliberating with @brave/uplift-approvers. QA has verified the PR on Nightly as per #8402 (comment).