chore: delete deprecated-packages directory and all references

These packages were moved to `deprecated-packages/` instead of being
fully deleted. They were excluded from the Lerna workspace and served no
build/publish/CI purpose. Remove them entirely and clean up all
references in config files (renovate, jest, eslint, prettier) and docs.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: serhalp

.eslintignore

@@ -17,18 +17,13 @@ e2e-tests
 examples
 integration-tests
 **/*.d.ts
-deprecated-packages
 
 packages/*/*.js
 packages/gatsby-source-shopify/**/*.js
 packages/gatsby-plugin-preload-fonts/prepare/*.js
 packages/gatsby/cache-dir/commonjs/**/*
 packages/gatsby-codemods/transforms
 packages/gatsby-source-graphql/batching
-deprecated-packages/gatsby-plugin-gatsby-cloud/components
-deprecated-packages/gatsby-plugin-gatsby-cloud/context
-deprecated-packages/gatsby-plugin-gatsby-cloud/models
-deprecated-packages/gatsby-plugin-gatsby-cloud/utils
 packages/gatsby-plugin-preact/fast-refresh
 
 packages/gatsby-source-wordpress/test-site/**

.prettierignore

@@ -1,7 +1,6 @@
 *.min.js
 **/node_modules/**
 flow-typed
-deprecated-packages
 
 # webfont demo styles
 **/specimen_files