cmd/keyify: delete

Keyify has been unmaintained for years and hasn't been updated to work
on Go modules. The same functionality exists in gopls.

Closes: gh-185

Author: dominikh

README.md

@@ -42,7 +42,6 @@ tool is accompanied by its own README, describing it in more detail.
 
 | Tool                                               | Description                                                             |
 |----------------------------------------------------|-------------------------------------------------------------------------|
-| [keyify](cmd/keyify/)                              | Transforms an unkeyed struct literal into a keyed one.                  |
 | [staticcheck](cmd/staticcheck/)                    | Go static analysis, detecting bugs, performance issues, and much more. |
 | [structlayout](cmd/structlayout/)                  | Displays the layout (field sizes and padding) of structs.               |
 | [structlayout-optimize](cmd/structlayout-optimize) | Reorders struct fields to minimize the amount of padding.               |