Issue title: staging env is being used for wallets
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## Description 
Seems as though the 0.55.3 build (and possibly before) are using the staging environment for Brave Rewards Wallets. Per discussion with @NejcZdovc they should be production wallets.


## Steps to Reproduce
Scenario 1: 

## Actual result:
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## Expected result:


## Reproduces how often: 
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## Brave version (chrome://version info)
<!--For installed build, please copy Brave, Revision and OS from chrome://version and paste here. If building from source please mention it along with chrome://version details-->


### Reproducible on current release:
<!--Does the issue reproduce on browser-laptop version as well? -->


### Website problems only:  
- Does the issue resolve itself when disabling Brave Shields? 
- Is the issue reproducible on the latest version of Chrome? 

### Additional Information
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 Comments: 
 Comment 0: initial work was done here https://github.com/brave/brave-core/pull/392
 Comment 1: Verified passed with

Brave | 0.55.10 Chromium: 70.0.3538.22 (Official Build) beta(64-bit)
-- | --
Revision | ac9418ba9c3bd7f6baaffa0b055dfe147e0f8364-refs/branch-heads/3538@{#468}
OS | Mac OS X

- confirmed Brave Rewards are using production not staging wallets
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