This fixes the following warning, when building with Clang ToT on
Windows:
```
[6668/7618] Building CXX object
tools\lldb\source\Plugins\Process\Windows\Common\CMakeFiles\lldbPluginProcessWindowsCommon.dir\TargetThreadWindows.cpp.obj
C:\src\git\llvm-project\lldb\source\Plugins\Process\Windows\Common\TargetThreadWindows.cpp(182,22):
warning: cast from 'FARPROC' (aka 'long long (*)()') to
'GetThreadDescriptionFunctionPtr' (aka 'long (*)(void *, wchar_t **)')
converts to incompatible function type [-Wcast-function-type-mismatch]
```
This is similar to: https://github.com/llvm/llvm-project/pull/97905
a819b0e55f