Remove redundant `.resx` files when updated `dotnet` ships.

[brettfo]

PR #3904 required that some .resx files be added to the src/buildfromsource/ directory. When a new dotnet sdk is shipped that has changes #3577 and #3607, then the .resx files (and their accompanying .fs files) should be removed.

[dsyme]

+100

[cartermp]

@brettfo Does this still need to be open?

[brettfo]

There are still some we need to keep around for the proto build and buildfromsource, so it should stay open a bit longer.

[TD5]

Does resolving this issue remove the need to manually copy any files at all across to src\buildfromsource\FSharp.Compiler.Private\ (as per DEVGUIDE.md)?

[brettfo]

Yes, once this is resolved that manual copy step will go away. It should be handled by my changes in #5842.

[cartermp]

@brettfo Now that we have an updated SDK we build against, can these files be removed?

[cartermp]

Closing this as we no longer have this directory in our source build.