Don't create temporary file in wxDebugReport ctor.

Just use wxFileName::GetTempDir() instead of creating a file in the temporary
directory and then using its path.

Closes #15103.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73672 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775