Closes #5030: Call out required minimum versions for depdencies in upgrade documentation

docs/installation/upgrading.md

@@ -4,8 +4,15 @@
 
 Prior to upgrading your NetBox instance, be sure to carefully review all [release notes](../../release-notes/) that have been published since your current version was released. Although the upgrade process typically does not involve additional work, certain releases may introduce breaking or backward-incompatible changes. These are called out in the release notes under the version in which the change went into effect.
 
-!!! note
-    Beginning with version 2.8, NetBox requires Python 3.6 or later.
+## Update Dependencies to Required Versions
+
+NetBox v2.9.0 and later requires the following:
+
+| Dependency | Minimum Version |
+|------------|-----------------|
+| Python     | 3.6             |
+| PostgreSQL | 9.6             |
+| Redis      | 4.0             |
 
 ## Install the Latest Code
 

docs/release-notes/version-2.9.md

@@ -13,6 +13,8 @@
 
 ## v2.9.0 (2020-08-21)
 
+**Note:** Redis 4.0 or later is required for this release.
+
 ### New Features
 
 #### Object-Based Permissions ([#554](https://github.com/netbox-community/netbox/issues/554))