Fix compatability matrix.

Plugin version 2.0.0 doesn't _require_ Java 17. When used with Gradle 8.x it will happily run on Java 11.

Author: big-andy-coates

README.md

@@ -35,13 +35,15 @@ An example application using this plugin is available [here](https://github.com/
 Compatibility
 ===
 
-| Plugin Version   | Gradle Versions | Java Version | Kotlin Version | Notes                                                        |
-| ---------------- | --------------- | ------------ | -------------- | ------------------------------------------------------------ |
-| - -> 1.8.12      | 5.+ -> 7.5.+    | 11+          | 1.0.+ -> 1.6.+ |                                                              |
-| 1.8.12 -> 1.8.13 | 5.+ -> 7.5.+    | 11+          | 1.0.+ -> 1.9.+ | Adds support for Kotlin 1.7 and above.                       |
-| 1.8.14           | 5.+ -> 7.6.+    | 11+          | 1.0.+ -> 1.9.+ | Fixes compatibility issue with Gradle 7.6                    |
+| Plugin Version   | Gradle Versions | Java Version | Kotlin Version | Notes                                                                                      |
+|------------------|-----------------|--------------|----------------|--------------------------------------------------------------------------------------------|
+| - -> 1.8.12      | 5.+ -> 7.5.+    | 11+          | 1.0.+ -> 1.6.+ |                                                                                            |
+| 1.8.12 -> 1.8.13 | 5.+ -> 7.5.+    | 11+          | 1.0.+ -> 1.9.+ | Adds support for Kotlin 1.7 and above.                                                     |
+| 1.8.14           | 5.+ -> 7.6.+    | 11+          | 1.0.+ -> 1.9.+ | Fixes compatibility issue with Gradle 7.6                                                  |
 | 1.8.15 -> 1.8.x  | 5.+ -> 8.6.+    | 11+          | 1.6.+ -> 1.9.+ | Fixes compatibility issues with Gradle 8.0.<br>Use JUnit v5.8.0 or above if using Gradle 8 |
-| 2.0.0            | 8.11.+ -> 9.+   | 17+          | 1.8.+ -> 2.x+  | Adds support for Gradle 9.x.<br>Minimum Java version raised to 17 |
+| 2.0.0            | 8.11.+ -> 9.+   | 11+ [^1]     | 1.8.+ -> 2.x+  | Adds support for Gradle 9.x.                                                                |
+
+[^1]: Gradle 9.x itself requires JDK 17+ to run, regardless of the plugin's own Java version support. See the [Gradle 9 upgrade guide](https://docs.gradle.org/current/userguide/upgrading_major_version_9.html). This applies to all plugin versions that support Gradle 9.x and above.
 
 Setup
 ===
@@ -956,7 +958,7 @@ Please file issues if you run into any problems or have additional requirements!
 Requirements
 ===
 
-This latest version of this plugin requires JDK 17 or newer to be used when running Gradle. Older versions support JDK 11.
+This plugin requires JDK 11 or newer to be used when running Gradle. If you use Gradle 9.x, JDK 17 or newer is required to run Gradle itself (see the [Compatibility](#compatibility) table above).
 
 The minimum Gradle version supported by this plugin is 5.1.
 However, we strongly recommend to use at least Gradle 6.0, because there are a few special cases that cannot be handled correctly when using older versions.