fix: tests looping toInitial.json data should run

[colinrotherham]

This PR fixes the Promise.all() calls in packages/postcss-reduce-initial/test/index.js so they resolve

cssnano/packages/postcss-reduce-initial/test/index.js

Lines 20 to 25 in c4be0f5

	Promise.all([
	processCSS(t, `${property}:${value}`, `${property}:initial`, {
	env: 'chrome58',
	}),
	passthroughCSS(t, `${property}:${value}`, { env: 'ie6' }),
	]);

Two property tests for 'writing-mode' and 'transform-box' failed but these were handled in:

• feat(postcss-reduce-initial): added ignore options #929
• fix(postcss-reduce-initial): regenerate data #1242

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.59%. Comparing base (6f9fa98) to head (492800b).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1572   +/-   ##
=======================================
  Coverage   97.59%   97.59%           
=======================================
  Files         123      124    +1     
  Lines       10325    10328    +3     
=======================================
+ Hits        10077    10080    +3     
  Misses        248      248           

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[colinrotherham]

@ludofischer Rebased to resolve the conflict 👍