fix(readme): clarify explanation

Author: deemp

README.md

@@ -207,7 +207,7 @@ This attrset contains the following attributes:
 - `usingFixesFrom` - `usingFixesFrom nixpkgsWithFixes` produces an attrset where particular extensions have fixes specified in the supplied `nixpkgsWithFixes` (see `mkExtensionNixpkgs` in [mkExtension.nix](./mkExtension.nix), [Versions with fixes from particular `nixpkgs`](#versions-with-fixes-from-particular-nixpkgs)).
   - The supplied `nixpkgsWithFixes` can be any version of `nixpkgs` (see [Get `nixpkgs`](#get-nixpkgs)).
   - The supplied `nixpkgsWithFixes` is used only to look up the fixes in its source code and is independent of the `nixpkgs` that you apply the overlay to.
-- The top-level `vscode-marketplace*` and `open-vsx*` attributes are constructed using fixes from `nixpkgs` that you apply the overlay to or `nixpkgs` from the `nix-vscode-extensions` repository and without usage of either `forVSCodeVersion` or `usingFixesFrom`.
+- The top-level `vscode-marketplace*` and `open-vsx*` attributes are constructed using fixes from `nixpkgs` that you apply the overlay to (if you [get `extensions` via the overlay](#get-extensions-via-the-overlay)) or `nixpkgs` from the `nix-vscode-extensions` repository (if you [get `extensions` from `nix-vscode-extensions`](#get-extensions-from-nix-vscode-extensions)).
 
 ### Extension identifiers