[clang-format] Fix CompactNamespaces corner case when...

[clang-format] Fix CompactNamespaces corner case when AllowShortLambdasOnASingleLine/BraceWrapping.BeforeLambdaBody are set

In clang-format 12, `CompactNamespaces` misformatted the code when `AllowShortLambdasOnASingleLine` is set to false and `BraceWrapping.BeforeLambdaBody` is true.

Input:
```
namespace out {
namespace in {
}
} // namespace out::in
```

Expected output:
```
namespace out { namespace in {
}} // namespace out::in
```

Output from v12:
```
namespace out {
namespace in {
}
} // namespace out::in
```

Config triggering the issue:
```
---
AllowShortLambdasOnASingleLine: None
BraceWrapping:
  BeforeLambdaBody :    true
BreakBeforeBraces: Custom
CompactNamespaces: true
...
```

Seems there's a corner case when `AllowShortLambdasOnASingleLine` is false, and `BraceWrapping.BeforeLambdaBody` is true, that causes CompactNamespaces to stop working.
The cause was a misannotation of `{` opening brace after `namespace` as a lambda opening brace.
The regression was probably introduced with [this commit](https://github.com/llvm/llvm-project/commit/fa0118e6e588fe303b08e7e06ba28ac1f8d50c68).

Originally contributed by Ahmed Mahdy (@aybassiouny). Thank you!

Reviewed By: Wawha, HazardyKnusperkeks

Differential Revision: https://reviews.llvm.org/D99031