update error message text for Gemini in the case where user attempts to link 2 Gemini wallets to same paymentID - follow up to #17569

[LaurenWags]

Description

Currently if a user attempts to connect 2 Gemini wallets to the same paymentID, an error is displayed, but it is generic and doesn't offer much information.

Uphold also has an error for this case and it provides more information (implemented with #16468 and #17271).
bitFlyer will get this more descriptive error message with #17592.

Steps to Reproduce

1. Clean install, staging env, non-Japan region. Enable Gemini in flags (if necessary) and restart.
2. Enable Rewards, link KYC'd Gemini wallet
3. Manually disconnect from Gemini (from wallet panel)
4. Confirm you are returned to pre-link state (UI, no balance, etc)
5. Link a second (different) KYC'd Gemini wallet
6. Logs show 403 linking error
7. UI shows generic error

Actual result:

Expected result:

Error message text should be more like that in the Uphold case:

Reproduces how often:

easily

Brave version (brave://version info)

Brave	1.30.43 Chromium: 93.0.4577.51 (Official Build) nightly (x86_64)
Revision	762d21050e2da59930c784c09b134d0b0b148188-refs/branch-heads/4577@{#915}
OS	macOS Version 11.5.2 (Build 20G95)

Version/Channel Information:

• Can you reproduce this issue with the current release? n/a
• Can you reproduce this issue with the beta channel? yes
• Can you reproduce this issue with the nightly channel? yes

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields?
• Does the issue resolve itself when disabling Brave Rewards?
• Is the issue reproducible on the latest version of Chrome?

Miscellaneous Information:

cc @Miyayes

[LaurenWags]

Verified passed with

Brave	1.31.29 Chromium: 93.0.4577.63 (Official Build) nightly (x86_64)
Revision	ff5c0da2ec0adeaed5550e6c7e98417dac77d98a-refs/branch-heads/4577@{#1135}
OS	macOS Version 11.5.2 (Build 20G95)

Verified STR from description. Confirmed new message displays for the case described.