Update notes on Reward.go

[evanorti]

Summary of changes

1. Updated notes to reflect the fact that oracle rewards come from spread fees, not from seigniorage.
2. Added note clarifying reward distribution ratio calculation for easy reference.

Report of required housekeeping

• [ ] Github issue OR spec proposal link
• [ ] Wrote tests
• [ ] Updated API documentation (client/lcd/swagger-ui/swagger.yaml)
• [ ] Added a relevant changelog entry: clog add [section] [stanza] [message]

---

(FOR ADMIN) Before merging

• [ ] Added appropriate labels to PR
• [ ] Squashed all commits, uses message "Merge pull request #XYZ: [title]" (coding standards)
• [ ] Confirm added tests are consistent with the intended behavior of changes
• [ ] Ensure all tests pass

[codecov[bot]]

Codecov Report

Merging #735 (02188ed) into main (6235f92) will increase coverage by 19.77%. The diff coverage is 86.18%.

@@             Coverage Diff             @@
##             main     #735       +/-   ##
===========================================
+ Coverage   44.81%   64.58%   +19.77%     
===========================================
  Files         122      100       -22     
  Lines        7016     4524     -2492     
===========================================
- Hits         3144     2922      -222     
+ Misses       3627     1387     -2240     
+ Partials      245      215       -30     

Impacted Files	Coverage Δ
app/export.go	0.00% <0.00%> (ø)
x/market/keeper/msg_server.go	0.00% <ø> (ø)
x/wasm/keeper/legacy_querier.go	61.44% <ø> (+26.21%)	:arrow_up:
x/wasm/keeper/querier.go	50.00% <ø> (+14.61%)	:arrow_up:
x/wasm/types/keys.go	0.00% <ø> (ø)
x/oracle/abci.go	89.83% <50.00%> (-10.17%)	:arrow_down:
x/oracle/keeper/reward.go	47.16% <50.00%> (ø)
x/oracle/tally.go	85.36% <50.00%> (-6.53%)	:arrow_down:
x/wasm/genesis.go	68.00% <71.42%> (+1.33%)	:arrow_up:
x/wasm/keeper/keeper.go	84.26% <78.94%> (+2.45%)	:arrow_up:
... and 42 more