Support deleting issues on github

[haji-ali]

I hope this is not a duplicate (my search did not reveal anything).

I noticed that deleting an issue on github makes the issue stuck/unmodifiable in forge. In the sense that it does not go away when fetching, and modifying it gives the error

error in process filter: ghub--graphql-handle-failure: GraphQL Error: ((type . "NOT_FOUND") (path "repository" "issue") (locations ((line . 3) (column . 5))) (message . "Could not resolve to an Issue with the number of 122."))
error in process filter: GraphQL Error: ((type . "NOT_FOUND") (path "repository" "issue") (locations ((line . 3) (column . 5))) (message . "Could not resolve to an Issue with the number of 122.")) 

magit version is Magit v4.4.0-25-g46e4b5d, Transient 0.10.0, Forge 0.6.0, Git 2.50.1, Emacs 29.4, darwin.

It would be great if there's a way to resolve this in one or another, short of deleting the database and re-fetching all issues.

[tarsius]

See forge-remove-topic-locally (including its docstring).