Wording improvements in WordPress AI Experiments plugin documentation

[mehrazmorshed]

This pull request refines wording in the WordPress AI Experiments plugin description to improve clarity and tone.

Changes include:

• Updated “inside WordPress” to “within WordPress” for a more formal style
• Reduced unnecessary repetition of “the” before “building blocks”

No functional changes were made; this update focuses solely on documentation quality.

[github-actions]

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Co-authored-by: mehrazmorshed <mehrazmorshed@git.wordpress.org>

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 46.89%. Comparing base (7dbbc44) to head (98cf9ce).
⚠️ Report is 33 commits behind head on develop.

Additional details and impacted files

@@            Coverage Diff             @@
##             develop     #161   +/-   ##
==========================================
  Coverage      46.89%   46.89%           
  Complexity       208      208           
==========================================
  Files             19       19           
  Lines           1271     1271           
==========================================
  Hits             596      596           
  Misses           675      675           

Flag	Coverage Δ
unit	46.89% <ø> (ø)

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