[clang-format] Ensure we can correctly parse lambda in the template argument list

https://github.com/llvm/llvm-project/issues/46505

The presence of a lambda in an argument template list ignored the [] as a lambda at all, this caused the contents of the <> to be incorrectly analyzed.

```
struct Y : X < [] {
  return 0;
} > {};
```
Fixes: #46505

Reviewed By: curdeius

Differential Revision: https://reviews.llvm.org/D116806