[`flake8-simplify`] Make example error out-of-the-box (`SIM116`) (#19111)

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## Summary

<!-- What's the purpose of the change? What does it do, and why? -->

Part of #18972

This PR makes [if-else-block-instead-of-dict-lookup
(SIM116)](https://docs.astral.sh/ruff/rules/if-else-block-instead-of-dict-lookup/#if-else-block-instead-of-dict-lookup-sim116)'s
example error out-of-the-box

[Old example](https://play.ruff.rs/718f17ee-fbe2-4520-97c6-153bc0f4502d)
```py
if x == 1:
    return "Hello"
elif x == 2:
    return "Goodbye"
else:
    return "Goodnight"
```

[New example](https://play.ruff.rs/8a9b47b4-da46-4a50-8576-362cdd707cee)
```py
def find_phrase(x):
    if x == 1:
        return "Hello"
    elif x == 2:
        return "Goodbye"
    elif x == 3:
        return "Good morning"
    else:
        return "Goodnight"
```

The "Use instead" section was also updated to reflect the new case. I
also changed it to use an intermediary variable since I find the `return
<long dict>.get` very ugly and hard to read.

## Test Plan

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

N/A, no functionality/tests affected

crates/ruff_linter/src/rules/flake8_simplify/rules/if_else_block_instead_of_dict_lookup.rs

@@ -18,17 +18,22 @@ use crate::checkers::ast::Checker;
 ///
 /// ## Example
 /// ```python
-/// if x == 1:
-///     return "Hello"
-/// elif x == 2:
-///     return "Goodbye"
-/// else:
-///     return "Goodnight"
+/// def find_phrase(x):
+///     if x == 1:
+///         return "Hello"
+///     elif x == 2:
+///         return "Goodbye"
+///     elif x == 3:
+///         return "Good morning"
+///     else:
+///         return "Goodnight"
 /// ```
 ///
 /// Use instead:
 /// ```python
-/// return {1: "Hello", 2: "Goodbye"}.get(x, "Goodnight")
+/// def find_phrase(x):
+///     phrases = {1: "Hello", 2: "Goodye", 3: "Good morning"}
+///     return phrases.get(x, "Goodnight")
 /// ```
 #[derive(ViolationMetadata)]
 pub(crate) struct IfElseBlockInsteadOfDictLookup;