docs: 📝 Updating the example for assert(S101) (#6986)

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## Summary

Rewriting the `if`-comparison to focus on the meaning of rule ` assert
S101`.

Fixes #6984

## Test Plan

<!-- How was it tested? -->

---------

Co-authored-by: Zanie Blue <contact@zanie.dev>

crates/ruff/src/rules/flake8_bandit/rules/assert_used.rs

@@ -23,6 +23,10 @@ use ruff_text_size::Ranged;
 ///
 /// Use instead:
 /// ```python
+/// if not x > 0:
+///     raise ValueError("Expected positive value.")
+///
+/// # or even better:
 /// if x <= 0:
 ///     raise ValueError("Expected positive value.")
 /// ```