Wrong editor is used for external C/C++ files

[ghentschke]

When an external C/C++ source file (like a system header) has to be opened via F3 (Open Declaration) from within the non-LSP-based (old) C/C++ editor:

and the new LSP based C/C++ editor has been set as default in the Content Type file associations:

then the external file is opened in the LSP based C/C++ editor:

Expected behavior:
When the parent source file (here: CppManaged.cpp) has been opened in the old C/C++ editor, the external header file should be opened in the old editor as well.