Removing back arrow in asset detail view, updating top buy link [crypto.com widget 1.17]

[ryanml]

Uplift of: #6942
Fixes: brave/brave-browser#12277, brave/brave-browser#12304

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]

Restarting iOS via https://ci.brave.com/job/pr-brave-browser-cdc-fixes-2-17-ios/2/ due to build failing as per https://ci.brave.com/job/pr-brave-browser-cdc-fixes-2-17-ios/1/execution/node/185/log.

22:12:14  FAILED: gen/brave/vendor/brave-ios/ads.mojom.objc.h gen/brave/vendor/brave-ios/ads.mojom.objc+private.h gen/brave/vendor/brave-ios/ads.mojom.objc.mm gen/brave/vendor/brave-ios/objc_templates_bytecode/ads_objc_templates.zip 

test-browser failed on macOS due to RewardsContributionBrowserTest.AutoContributeWhenACOff failing as per https://ci.brave.com/job/pr-brave-browser-cdc-fixes-2-17-macos/1/execution/node/249/log/. However, this is a known intermittent issue and doesn't block uplift.

23:01:33  1 test crashed:
23:01:33      RewardsContributionBrowserTest.AutoContributeWhenACOff (../../brave/components/brave_rewards/browser/test/rewards_contribution_browsertest.cc:259)

[kjozwiak]

Uplift into 1.17.x approved after deliberating with @brave/uplift-approvers. QA & @rebron have verified the PR on Nightly as per #6942 (comment) & #6942 (comment).