Removed unused variable in TRY300's example (#10190)

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## Summary

Removes the unnecessary `exc` variable in `TRY300`'s docs example.

## Test Plan
```
python scripts/generate_mkdocs.py; mkdocs serve -f mkdocs.public.yml
```

crates/ruff_linter/src/rules/tryceratops/rules/try_consider_else.rs

@@ -25,7 +25,7 @@ use crate::checkers::ast::Checker;
 ///         rec = 1 / n
 ///         print(f"reciprocal of {n} is {rec}")
 ///         return rec
-///     except ZeroDivisionError as exc:
+///     except ZeroDivisionError:
 ///         logging.exception("Exception occurred")
 /// ```
 ///
@@ -37,7 +37,7 @@ use crate::checkers::ast::Checker;
 /// def reciprocal(n):
 ///     try:
 ///         rec = 1 / n
-///     except ZeroDivisionError as exc:
+///     except ZeroDivisionError:
 ///         logging.exception("Exception occurred")
 ///     else:
 ///         print(f"reciprocal of {n} is {rec}")