Fix #6967: Use constants provided by core for Solana Instruction Decoding

[StephenHeaps]

Summary of Changes

• Small code re-use now that these String constants are available via core.

This pull request fixes #6967

Submitter Checklist:

• Unit Tests are updated to cover new or changed functionality
• User-facing strings use NSLocalizableString()
• New or updated UI has been tested across:
  • Light & dark mode
  • Different size classes (iPhone, landscape, iPad)
  • Different dynamic type sizes

Test Plan:

Verify code changes matches up with new constants: https://github.com/brave/brave-core/blob/master/components/brave_wallet/common/brave_wallet.mojom#L1678-L1685

Screenshots:

Reviewer Checklist:

• Issues include necessary QA labels:
  • QA/(Yes|No)
  • bug / enhancement
• Necessary security reviews have taken place.
• Adequate unit test coverage exists to prevent regressions.
• Adequate test plan exists for QA to validate (if applicable).
• Issue and pull request is assigned to a milestone (should happen at merge time).

[soner-yuksel]

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