Problem: currently in the example a new diagnostic namespace is created
for showing it manually with a custom config. Because of a separate
namespace, when the original diagnostic source sets diagnostics again,
it will not affect the diagnostic shown in that new namespace and the
user would need to implement the logic for hiding it themselves,
separately as well.
Solution: instead of creating a new namespace, reuse the original
diagnostic's namespace, so once the source sets diagnostics again, it's
removed and hidden automatically without user having to do anything
extra for that.