Deal with portal_quickinstaller deprecation and removal

Author: stevepiercy

docs/backend/upgrading/add-on-upgrade.md

@@ -30,8 +30,13 @@ This chapter describes the steps to migrate your third party products.
 -   Perform product-specific upgrade procedures, if any.
     You will find these in the documentation of each product.
 
-If `/prefs_install_products_form` is unreachable, you should try doing the add-on upgrades from the Management Interface.
-Navigate to the quickinstaller in the Management Interface, and reinstall or upgrade products that are shown to be outdated.
+If `/prefs_install_products_form` is unreachable, and you are using Plone 5.0.x or earlier, you should try doing the add-on upgrades from the Management Interface.
+Navigate to the `portal_quickinstaller` in the Management Interface at `/portal_quickinstaller/manage_installProductsForm`, and reinstall or upgrade products that are shown to be outdated.
+
+```{versiondeprecated} 5.1
+`portal_quickinstaller` was deprecated in Plone 5.1, and was removed in Plone 6.0.
+See [PLIP 1775](https://github.com/plone/Products.CMFPlone/issues/1775) and {ref}`upgrade-5.1-do-not-use-portal_quickinstaller-label` for Plone 5.1 and later.
+```
 
 ```{warning}
 Be careful when updating add-ons through the Management Interface.

docs/backend/upgrading/version-specific-migration/upgrade-addons-to-51.md

@@ -85,6 +85,8 @@ An uninstall profile is a profile that is registered with the name `uninstall`.
 See https://github.com/plone/plone.app.multilingual/tree/master/src/plone/app/multilingual/profiles/uninstall.
 
 
+(upgrade-5.1-do-not-use-portal_quickinstaller-label)=
+
 ### Do Not Use `portal_quickinstaller`
 
 Old code:

docs/backend/upgrading/version-specific-migration/upgrade-to-51.md

@@ -129,7 +129,7 @@ See for example [pas.plugins.authomatic](https://pypi.org/project/pas.plugins.au
 If you want to use this in your site, you must add `plone.app.openid` to the buildout eggs.
 
 
-### portal_quickinstaller Deprecated
+### `portal_quickinstaller` Deprecated
 
 This is [PLIP 1340](https://github.com/plone/Products.CMFPlone/issues/1340).
 

docs/backend/upgrading/version-specific-migration/upgrade-to-60.md

@@ -17,7 +17,7 @@ Some may require changes in your setup.
 
 (v60-removed-portal_quickinstaller-label)=
 
-## Removed portal_quickinstaller
+## Removed `portal_quickinstaller`
 
 Plone no longer ships with the `portal_quickinstaller` tool (`CMFQuickInstallerTool`).
 In existing sites, the standard upgrade will remove the tool.