fix(config): remove unsupported nullish coalescing

[danielroe]

Types of changes

• Bug fix (a non-breaking change which fixes an issue)

Description

• issue introduced in feat(config): support nuxtrc in dist directory #9280

closes #9321

Checklist:

• All new and existing tests are passing.

[codecov-commenter]

Codecov Report

Merging #9322 (6735bf0) into dev (c56d484) will increase coverage by 0.04%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##              dev    #9322      +/-   ##
==========================================
+ Coverage   65.13%   65.17%   +0.04%     
==========================================
  Files          94       94              
  Lines        4101     4106       +5     
  Branches     1124     1123       -1     
==========================================
+ Hits         2671     2676       +5     
  Misses       1152     1152              
  Partials      278      278              

Flag	Coverage Δ
unittests	65.17% <100.00%> (+0.04%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
packages/config/src/load.js	76.84% <100.00%> (+1.28%)	⬆️

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[pi0]

(pending to check possibility of adding esbuild to build scripts to avoid accidental syntax usage in the future) ~> #9328