Lower the ConnMgr.HighWater and LowWater limits (uplift to 1.19.x)

[brave-builds]

Uplift of #7577
Resolves brave/brave-browser#13525

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.

[kjozwiak]

Win failed due to several test-browser failures as per https://ci.brave.com/job/pr-brave-browser-pr7577_ipfs-high-low-water_1.19.x-windows/1/execution/node/214/log/. However, these are known intermittent issues as per brave/brave-browser#12987, brave/brave-browser#12607, brave/brave-browser#12704, brave/brave-browser#12985, brave/brave-browser#12607, brave/brave-browser#12605 & brave/brave-browser#12632.

16:22:52  7 tests failed:
16:22:52      RewardsBrowserTest.BackupRestoreModalHasNotice (../../brave/components/brave_rewards/browser/test/rewards_browsertest.cc:304)
16:22:52      RewardsBrowserTest.ResetRewardsWithBAT (../../brave/components/brave_rewards/browser/test/rewards_browsertest.cc:375)
16:22:52      RewardsBrowserTest.UpholdLimitNoBAT (../../brave/components/brave_rewards/browser/test/rewards_browsertest.cc:398)
16:22:52      RewardsContributionBrowserTest.TipConnectedPublisherVerified (../../brave/components/brave_rewards/browser/test/rewards_contribution_browsertest.cc:586)
16:22:52      RewardsContributionBrowserTest.TipUnverifiedPublisher (../../brave/components/brave_rewards/browser/test/rewards_contribution_browsertest.cc:304)
16:22:52      RewardsPromotionBrowserTest.ClaimViaSettingsPage (../../brave/components/brave_rewards/browser/test/rewards_promotion_browsertest.cc:196)
16:22:52      RewardsPromotionBrowserTest.PromotionRemovedFromEndpoint (../../brave/components/brave_rewards/browser/test/rewards_promotion_browsertest.cc:231)

macOS failed test-browser due to several reward failures as per https://ci.brave.com/job/pr-brave-browser-pr7577_ipfs-high-low-water_1.19.x-macos/1/execution/node/201/log/. However, as per above, these are known intermittent issues that don't block uplift.

17:21:48  2 tests failed:
17:21:48      RewardsBrowserTest.UpholdLimitNoBAT (../../brave/components/brave_rewards/browser/test/rewards_browsertest.cc:398)
17:21:48      RewardsPromotionBrowserTest.ClaimViaPanel (../../brave/components/brave_rewards/browser/test/rewards_promotion_browsertest.cc:202)

[kjozwiak]

Uplift into 1.19.x approved after deliberating with @brave/uplift-approvers. QA has verified the PR on Nightly as per #7577 (comment).