[CORDA-3442] Update app upgrade notes for gradle version for PV5 (#5740)

* [CORDA-3442] Update app upgrade notes for gradle version for PV5

* [CORDA-3442] Adjust a link and add some backticks

docs/source/app-upgrade-notes.rst

@@ -85,6 +85,26 @@ To fix this, an explicit type hint must be provided to the compiler:
 
 This stops type inference from occurring and forces the variable to be of type ``AbstractParty``.
 
+.. _platform_version_5_gradle_changes:
+
+Step 2. Update Gradle version and associated dependencies
+---------------------------------------------------------
+
+Platform Version 5 requires Gradle 5.4 to build. If you use the Gradle wrapper, you can upgrade by running:
+
+ .. code:: shell
+
+        ./gradlew wrapper --gradle-version 5.4.1
+
+Otherwise, upgrade your installed copy in the usual manner for your operating system.
+
+Additionally, you'll need to add https://repo.gradle.org/gradle/libs-releases as a repository to your project, in order to pick up the
+`gradle-api-tooling` dependency. You can do this by adding the following to the repositories in your Gradle file:
+
+.. code-block:: groovy
+
+    maven { url 'https://repo.gradle.org/gradle/libs-releases' }
+
 Upgrading apps to Platform Version 4
 ====================================
 
@@ -124,6 +144,10 @@ You should also ensure you're using Gradle 4.10 (but not 5). If you use the Grad
 
 Otherwise just upgrade your installed copy in the usual manner for your operating system.
 
+.. note:: Platform Version 5 requires a different version of Gradle, so if you're intending to upgrade past Platform Version 4 you may wish
+   to skip updating Gradle here and upgrade directly to the version required by Platform Version 5. You'll still need to alter the version
+   numbers in your Gradle file as shown in this section. See :ref:`platform_version_5_gradle_changes`
+
 Step 3. Update your Gradle build file
 -------------------------------------