Fix global-state-schema key name in REST API spec

[algorandskiy]

Summary

Follows up this PR in dev docs: algorandfoundation/docs#569

[codecov-commenter]

Codecov Report

Merging #2972 (18ce94e) into master (1202d32) will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2972      +/-   ##
==========================================
- Coverage   47.62%   47.61%   -0.02%     
==========================================
  Files         358      358              
  Lines       57906    57906              
==========================================
- Hits        27576    27570       -6     
- Misses      27207    27212       +5     
- Partials     3123     3124       +1     

Impacted Files	Coverage Δ
cmd/algoh/blockWatcher.go	77.77% <0.00%> (-3.18%)	⬇️
catchup/service.go	69.35% <0.00%> (-0.78%)	⬇️
network/wsPeer.go	74.37% <0.00%> (-0.56%)	⬇️
network/wsNetwork.go	60.90% <0.00%> (-0.19%)	⬇️
ledger/acctupdates.go	63.19% <0.00%> (-0.09%)	⬇️
network/requestTracker.go	71.12% <0.00%> (+0.86%)	⬆️
ledger/blockqueue.go	82.18% <0.00%> (+1.14%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 1202d32...18ce94e. Read the comment docs.