Update index.yml

Author: Chukslord1

learn-pr/github/github-actions-ci/index.yml

@@ -38,8 +38,8 @@ units:
 - learn.github.github-actions-ci.1-introduction
 - learn.github.github-actions-ci.2-github-actions-workflows-ci
 - learn.github.github-actions-ci.github-actions-manage-and-debug-workflow
-- learn.github.github-actions-ci.2c-github-actions-essential-features
-- learn.github.github-actions-ci.2d-cache-share-debug-workflows
+- learn.github.github-actions-ci.github-actions-essential-features
+- learn.github.github-actions-ci.cache-share-debug-workflows
 - learn.github.github-actions-ci.3-exercise-ci-workflow-github
 - learn.github.github-actions-ci.4-knowledge-check
 - learn.github.github-actions-ci.5-summary