[clang-tools-extra] [clang-tidy] Fix readability-simplify-boolean-expr for init statements (PR #172220)

[Yanzuo Liu via cfe-commits]

zwuis wrote:

> Closes #172180

Should be removed.

```cpp
if (bool b = ...; b == true) { ... }
// target in that issue
if (bool b = ...) { ... }
// what this PR does currently (from tests)
if (bool b = ...; b) { ... }
```

https://github.com/llvm/llvm-project/pull/172220