remove useless "readyPackages" (#6319)

## What's the problem this PR addresses?

<!-- Describe the rationale of your PR. -->
<!-- Link all issues that it closes. (Closes/Resolves #xxxx.) -->

...

In `linkEverything` function, there is a variable called
"readyPackages". But it's never actually used in the code. Remove it.

## How did you fix it?

<!-- A detailed description of your implementation. -->

...

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---------

Co-authored-by: Maël Nison <nison.mael@gmail.com>

.yarn/versions/91acd0ec.yml

@@ -0,0 +1,34 @@
+releases:
+  "@yarnpkg/core": patch
+
+declined:
+  - "@yarnpkg/plugin-compat"
+  - "@yarnpkg/plugin-constraints"
+  - "@yarnpkg/plugin-dlx"
+  - "@yarnpkg/plugin-essentials"
+  - "@yarnpkg/plugin-exec"
+  - "@yarnpkg/plugin-file"
+  - "@yarnpkg/plugin-git"
+  - "@yarnpkg/plugin-github"
+  - "@yarnpkg/plugin-http"
+  - "@yarnpkg/plugin-init"
+  - "@yarnpkg/plugin-interactive-tools"
+  - "@yarnpkg/plugin-link"
+  - "@yarnpkg/plugin-nm"
+  - "@yarnpkg/plugin-npm"
+  - "@yarnpkg/plugin-npm-cli"
+  - "@yarnpkg/plugin-pack"
+  - "@yarnpkg/plugin-patch"
+  - "@yarnpkg/plugin-pnp"
+  - "@yarnpkg/plugin-pnpm"
+  - "@yarnpkg/plugin-stage"
+  - "@yarnpkg/plugin-typescript"
+  - "@yarnpkg/plugin-version"
+  - "@yarnpkg/plugin-workspace-tools"
+  - "@yarnpkg/builder"
+  - "@yarnpkg/cli"
+  - "@yarnpkg/doctor"
+  - "@yarnpkg/extensions"
+  - "@yarnpkg/nm"
+  - "@yarnpkg/pnpify"
+  - "@yarnpkg/sdks"

packages/yarnpkg-core/sources/Project.ts

@@ -1471,12 +1471,8 @@ export class Project {
     for (const [, explain] of miscUtils.sortMap(skippedBuildLogs, ([locator]) => structUtils.stringifyLocator(locator)))
       explain(report);
 
-    const readyPackages = new Set(this.storedPackages.keys());
     const buildablePackages = new Set(packageBuildDirectives.keys());
 
-    for (const locatorHash of buildablePackages)
-      readyPackages.delete(locatorHash);
-
     const globalHashGenerator = createHash(`sha512`);
     globalHashGenerator.update(process.versions.node);