fix: make all filter operators uppercase

[villebro]

🐛 Bug Fix

Currently unary operators are uppercase, while binary and set operators are lowercase, which looks weird. As of PR 9556 Superset now expects all filter operators to be uppercase (it does work with lowercase, but this support might be removed at some point).

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[codecov]

Codecov Report

Merging #378 into master will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #378   +/-   ##
=======================================
  Coverage   26.35%   26.35%           
=======================================
  Files         192      192           
  Lines        5256     5256           
  Branches      459      459           
=======================================
  Hits         1385     1385           
  Misses       3842     3842           
  Partials       29       29           

Impacted Files	Coverage Δ
packages/superset-ui-query/src/types/Operator.ts	100.00% <100.00%> (ø)

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