fix: false values are removed from style string. closes #1692

[mlrawlings]

Description

<div style={ display: "block", color: false, marginRight: 16 }>

Old output

<div style="display:block;color:false;margin-right:16px;">

New output

<div style="display:block;margin-right:16px;">

Checklist:

• I have read the CONTRIBUTING document and have signed (or will sign) the CLA.
• I have updated/added documentation affected by my changes.
• I have added tests to cover my changes.

[codecov]

Codecov Report

Merging #1693 (03946b1) into main (5de6157) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #1693   +/-   ##
=======================================
  Coverage   90.43%   90.43%           
=======================================
  Files         222      222           
  Lines        6733     6733           
=======================================
  Hits         6089     6089           
  Misses        644      644           

Impacted Files	Coverage Δ
packages/marko/src/runtime/helpers/style-value.js	95.00% <100.00%> (ø)

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