MAINT: Replace pejorative wording in a test comment

[mmcky]

Problem

quantecon/tests/test_lqnash.py:95 contains a comment using "ghetto" as a pejorative. The word carries a racial connotation and has no place in a widely-forked teaching library. The underlying concern — that hardcoded MATLAB reference values are an unsatisfying way to fix expected outputs — is legitimate and worth keeping, just phrased plainly.

A one-word fix, and a reasonable first contribution.

Acceptance criteria

• The comment is rewritten to state the actual concern about hardcoded MATLAB reference values
• A quick grep confirms no similar wording elsewhere in the tree

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From the July 2026 technical-debt audit (AI-assisted; claims verified against 28d4b3b on 2026-07-25).

[jasperdingg]

I'd love to take this as my first contribution, may I be assigned?