chore: Remove dead packages
Created by: efritz
Remaining lint:
$ ./depgraph lint NoDeadPackages
error: 5 errors:
(NoDeadPackages) cmd/frontend/external
(NoDeadPackages) doc/cli/references
(NoDeadPackages) enterprise/internal/codeintel/lsif/repl
(NoDeadPackages) internal/goremancmd
(NoDeadPackages) internal/version/minversion