docs: add back-link from remove-submodule to parent recipe

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: braboj

chapters/recipes/remove-submodule.md

@@ -40,3 +40,6 @@ $ git commit -m "Remove submodule"
   run. Use `--force` if you are certain the changes are not needed.
 - **Nested submodules** — if the submodule itself contains submodules,
   you need to deinit recursively or clean up `.git/modules/` manually.
+
+For other submodule operations, see the [Submodules](submodules.md)
+recipe.