fix keep alive flag value (uplift to 1.25.x)

[brave-builds]

Uplift of #8787
Resolves brave/brave-browser#15815

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 audit-deps due to several warning(s) as per https://ci.brave.com/job/pr-brave-browser-pr8787_keep-alive-flag_1.25.x-post-init/1/execution/node/144/log/. However, the warning(s) are known and unrelated to this specific PR.

test-browser failed on Linux as per https://ci.brave.com/job/pr-brave-browser-pr8787_keep-alive-flag_1.25.x-linux/1/testReport/. However, these are known intermittent failures and unrelated to this specific PR.

BraveAdsBrowserTest/BraveAdsUpgradeBrowserTest.UpgradePath/PreferencesForVersion072WithRewardsAndAdsEnabled_ForSupportedLocale_ForNewlySupportedLocale_RewardsShouldBeEnabled_AdsShouldBeDisabled
linux / test-browser / BraveAdsBrowserTest/BraveAdsUpgradeBrowserTest.UpgradePath/PreferencesForVersion072WithRewardsAndAdsEnabled_ForSupportedLocale_ForUnsupportedLocale_RewardsShouldBeEnabled_AdsShouldBeEnabled
linux / test-browser / BraveAdsBrowserTest/BraveAdsUpgradeBrowserTest.UpgradePath/PreferencesForVersion072WithRewardsAndAdsEnabled_ForUnsupportedLocale_ForUnsupportedLocale_RewardsShouldBeEnabled_AdsShouldBeDisabled
linux / test-browser / RewardsContributionBrowserTest.AutoContributionMultiplePublishersUphold
linux / test-browser / RewardsPublisherBrowserTest.VisitRegisteredPublisher

[kjozwiak]

Uplift into 1.25.x approved after deliberating with @brave/uplift-approvers. QA has verified the PR on Nightly as per #8787 (comment).