Complete work on moving content from install-backend-from-packages-step-by-step.md to manage-add-ons-packages.md

Author: stevepiercy

docs/install/index.md

@@ -101,6 +101,5 @@ System requirements depend upon your choice of installation method.
 
 containers/index
 install-from-packages
-install-backend-from-packages-step-by-step
 manage-add-ons-packages
 ```

docs/install/install-backend-from-packages-step-by-step.md

@@ -177,7 +177,7 @@ make install
 
 This will take a few minutes.
 ☕️
-First the backend, then the frontend are installed.
+First the backend, then the frontend will be installed.
 At the start of the frontend installation part, you might see a prompt.
 
 ```console