improve instructions on setting eas.projectId in app.json

[dsokal]

Before and after (IMO looks better):

[github-actions[bot]]

Size Change: -569 B (0%)

Total Size: 40.9 MB

Filename	Size	Change
./packages/eas-cli/dist/eas-linux-x64.tar.gz	40.9 MB	-569 B (0%)

_{compressed-size-action}

[codecov[bot]]

Codecov Report

Merging #1316 (f52ff9b) into main (e0a9384) will decrease coverage by 0.01%. The diff coverage is 0.00%.

:exclamation: Current head f52ff9b differs from pull request most recent head 4e797c8. Consider uploading reports for the commit 4e797c8 to get more accurate results

@@            Coverage Diff             @@
##             main    #1316      +/-   ##
==========================================
- Coverage   51.56%   51.55%   -0.00%     
==========================================
  Files         399      399              
  Lines       14118    14120       +2     
  Branches     2943     2943              
==========================================
  Hits         7278     7278              
- Misses       6312     6314       +2     
  Partials      528      528              

Impacted Files	Coverage Δ
packages/eas-cli/src/project/projectUtils.ts	67.70% <0.00%> (-1.05%)	:arrow_down:

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[dsokal]

/changelog-entry chore Improve instructions on setting extra.eas.projectId in app configuration.