Update CONTRIBUTING.md

remove outdated info about Everything.agda

Author: maxsnew

CONTRIBUTING.md

@@ -103,10 +103,6 @@ When preparing a PR here are some general guidelines:
   as well as various versions of function extensionality in
   [FunExtEquiv.agda](https://github.com/agda/cubical/blob/master/Cubical/Functions/FunExtEquiv.agda).
 
-- Unless a file is in the `Core`, `Foundations` or `Codata` package you
-  don't need to add it manually to the `Everything` file as it is
-  automatically generated when running `make`.
-
 - For folders with `Base` and `Properties` submodules, the `Base` file
   can contain some basic consequences of the main definition, but
   shouldn't include theorems that would require additional imports.