src: fix -Wreturn-stack-address error

[codebytere]

Refs #57016

Fixes the following:

../../third_party/electron_node/src/node_config_file.cc:26:16: error: returning address of local temporary object [-Werror,-Wreturn-stack-address]
   26 |         return it->substr(flag_path.size() + 1);
      |                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 90.19%. Comparing base (5ffcf6b) to head (3d0c700).
Report is 53 commits behind head on main.

Files with missing lines	Patch %	Lines
src/node_config_file.cc	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #58439      +/-   ##
==========================================
- Coverage   90.22%   90.19%   -0.03%     
==========================================
  Files         635      635              
  Lines      187173   187224      +51     
  Branches    36747    36770      +23     
==========================================
  Hits       168870   168870              
- Misses      11071    11120      +49     
- Partials     7232     7234       +2     

Files with missing lines	Coverage Δ
src/node_config_file.cc	73.38% <0.00%> (ø)

... and 59 files with indirect coverage changes

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[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/67034/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/67092/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/67157/

[nodejs-github-bot]

Landed in 47081ee