Fetches grants after wallet recovery

[ryanml]

Fixes: brave/brave-browser#4220

This also removes arguments that were never being used for the RewardsService::FetchGrants call.

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Test Plan:

Defined in issue

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[NejcZdovc]

@ryanml recovery response should return grants as you can see here https://github.com/brave/brave-core/pull/2372/files#diff-2e09ca2971f3a4e74fb753ef2fca3113R133. Let's try to figure out why grants are not correct instead of adding another get

[ryanml]

@NejcZdovc those are assigned under walletInfo, which are grants already claimed. We need to get grants available for claiming, which exists at the top level of the state.

[NejcZdovc]

@ryanml sounds good

[NejcZdovc]

@ryanml could you please add unit test for this reducer