[clang-format] Clang bug with formatting enum

The error was first introduced at https://github.com/llvm/llvm-project/pull/194154.

With a simple reproducer at:

```c++
enum Flags {
FLAG_WIN_NO_EXECUTE =
1 << 21, // Windows only. Marks the file with a deny ACE that prevents
// opening the file with EXECUTE access. Cannot be used with
// FILE_WIN_EXECUTE flag. See also PreventExecuteMapping.
};
```

When executing the clang formatter, this becomes:

```c++
// Minimal reproducer for clang-format enum line-breaking regression.
enum Flags {
FLAG_WIN_NO_EXECUTE = 1
<< 21, // Windows only. Marks the file with a deny ACE that prevents
// opening the file with EXECUTE access. Cannot be used with
// FILE_WIN_EXECUTE flag. See also PreventExecuteMapping.
};
```

Seems like the issue is at:

```c++
// clang/lib/Format/TokenAnnotator.cpp
if (!Scopes.empty() && Scopes.back() == ST_Enum)
Tok->setFinalizedType(TT_EnumEqual);
```

Because this is checking if there should be a value after = within the context of Enum.

Reproduce the enum formatting regression from the issue, then inspect clang/lib/Format/TokenAnnotator.cpp at the shown ST_Enum and TT_EnumEqual logic. Verify the formatter's output for the provided C++ example and trace how the enum assignment and shift expression are classified. Done means the example formats correctly without moving the shift operator onto a separate line.

Written by the indexing model from the issue text.