Fix buttons not working in IPFS interstitial page (uplift to 1.19.x)

[brave-builds]

Uplift of #7585
Resolves brave/brave-browser#13544

Approved, please ensure that before merging:

• You have checked CI and the builds, lint, and tests all pass or are not related to your PR.
• You have tested your change on Nightly.
• The PR milestones match the branch they are landing to.

After you merge:

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

[yrliou]

CI builds are green expect for Windows which has unrelated rewards browser test failures.

[2021-01-13T21:51:18.031Z]     RewardsBrowserTest.BackupRestoreModalHasNotice (../../brave/components/brave_rewards/browser/test/rewards_browsertest.cc:304)

[2021-01-13T21:51:18.031Z]     RewardsBrowserTest.ResetRewardsWithBAT (../../brave/components/brave_rewards/browser/test/rewards_browsertest.cc:375)

[2021-01-13T21:51:18.031Z]     RewardsBrowserTest.UpholdLimitNoBAT (../../brave/components/brave_rewards/browser/test/rewards_browsertest.cc:398)

[2021-01-13T21:51:18.031Z]     RewardsContributionBrowserTest.TipConnectedPublisherVerified (../../brave/components/brave_rewards/browser/test/rewards_contribution_browsertest.cc:586)

[2021-01-13T21:51:18.031Z]     RewardsContributionBrowserTest.TipUnverifiedPublisher (../../brave/components/brave_rewards/browser/test/rewards_contribution_browsertest.cc:304)

[2021-01-13T21:51:18.031Z]     RewardsPromotionBrowserTest.ClaimViaSettingsPage (../../brave/components/brave_rewards/browser/test/rewards_promotion_browsertest.cc:196)

[2021-01-13T21:51:18.031Z]     RewardsPromotionBrowserTest.PromotionRemovedFromEndpoint (../../brave/components/brave_rewards/browser/test/rewards_promotion_browsertest.cc:231)

[kjozwiak]

Uplift into 1.19.x approved after deliberating with @brave/uplift-approvers. QA has verified the PR on Nightly as per #7585 (comment).