fix: remove size utility

[gregberge]

Fix #177

Yes, it is a breaking change, but since v2 has not yet been widely adopted, I think it is possible to remove it. I assume it can break some code but the risk is not so big. It was a mistake adding size in v2.

[codecov]

Codecov Report

Merging #183 (3f0ba64) into master (f980ddb) will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #183      +/-   ##
==========================================
- Coverage   90.94%   90.93%   -0.01%     
==========================================
  Files          56       56              
  Lines        1005     1004       -1     
  Branches      185      185              
==========================================
- Hits          914      913       -1     
  Misses         90       90              
  Partials        1        1              

Impacted Files	Coverage Δ
packages/system/src/styles/sizing.ts	100.00% <ø> (ø)

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