[fixer-selftest] Fix comment typo in solve_eqs.cpp: "reprsents" → "represents" (#9924)

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## The fix

A single, objectively-correct spelling fix in a **code comment** (the
header comment block of the file — not code, identifiers, or string
literals).

- **File:** `src/ast/simplifiers/solve_eqs.cpp` (line 23, inside the
`/*++ ... --*/` header comment)
- **Before:** `... where bitset reprsents set of free variables.`
- **After:** `... where bitset represents set of free variables.`

The diff is a single line:

```diff
-1. maintain map FV: term -> bit-set where bitset reprsents set of free variables. Assume the number of variables is bounded.
+1. maintain map FV: term -> bit-set where bitset represents set of free variables. Assume the number of variables is bounded.
```

## Why this is safe

The change is **comment-only** and therefore **cannot affect z3's
behaviour or output** — so it needs **no rebuild and no testing** to be
confident it is correct. Nothing outside the comment text was touched
(no code, no string literals, no identifiers, no whitespace elsewhere).

## For maintainers

This is a genuine, correct fix, so feel free to **merge** it — but you
may also simply **close** it. The self-test's success does not depend on
this PR being merged; it only depends on the PR having been opened.




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Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/ast/simplifiers/solve_eqs.cpp

@@ -20,7 +20,7 @@ It traverses the same sub-terms many times.
 
 Outline of a presumably better scheme:
 
-1. maintain map FV: term -> bit-set where bitset reprsents set of free variables. Assume the number of variables is bounded.
+1. maintain map FV: term -> bit-set where bitset represents set of free variables. Assume the number of variables is bounded.
    FV is built from initial terms.
 2. maintain parent: term -> term-list of parent occurrences.
 3. repeat