Fixes link to point to training_collections/ (#671)

* Fixes link to point to training_collections/

* Revert "Fixes link to point to training_collections/"

This reverts commit a74885e.

* Fixes the link to training_collections/

* Applies final touches to the training collections block

* Update docs/index.md

Author: mribeirodantas

docs/index.md

@@ -122,9 +122,9 @@ These are materials that cover advanced concepts and mechanisms for developing a
 
         :material-compass:{.nextflow-primary} Collections of Side Questions grouped around a particular theme or use case.
 
-    Training Collections combine multiple Side Quests in order to provide a comprehensive learning experience around a particular around a common theme or use case.
+    Training Collections combine multiple Side Quests in order to provide a comprehensive learning experience around a particular theme or use case.
 
-    [Start the Side Quests training :material-arrow-right:](side_quests/){ .md-button .md-button--primary }
+    [Browse the Training Collections :material-arrow-right:](training_collections/){ .md-button .md-button--primary }
 
 ## Archived materials