Shows total amount to be received in a Gemini sell order

[ryanml]

Fixes brave/brave-browser#11046

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Spec in issue

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[emerick]

LGTM, just had a couple of minor comments

[kjozwiak]

Verification PASSED on macOS 10.15.6 x64 using the following build:

Brave | 1.14.44 Chromium: 85.0.4183.69 (Official Build) nightly (64-bit)
-- | --
Revision | 4554ea1a1171bd8d06951a4b7d9336afe6c59967-refs/branch-heads/4183@{#1426}
OS | macOS Version 10.15.6 (Build 19G73)

• Verified the STR/Cases via Updates Oauth scopes for Gemini #6280 (comment)
• ensured that the Total Received was being displayed on Sell Orders

Unfortunately I don't have a bank account linked so can't check the buy screen. QA or @ryanml will check the Buy screen once this lands in 1.13.x.