Update docs for -release to make it clear it accepts recent Java versions

The old displayed values of `6, 7, 8, 9` are confusing for developers contemplating updating to recent Java versions like `21` - eg from https://github.com/guardian/mobile-save-for-later/pull/109/files#r1559390842 :

> I was getting an error that -release:21 is not a valid compiler option when I ran the code. Looking at the docs: https://docs.scala-lang.org/overviews/compiler-options/ my understanding is that this is not supported for Java 21.

That's wrong, as newer Java versions definitely are supported by the `-release` Scala compiler parameter - so it's best to clarify that!

Author: rtyley

_data/compiler-options.yml

@@ -260,7 +260,7 @@
       type: "String"
       arg: "release"
       default:
-    description: "Compile for a specific version of the Java platform. Supported targets: 6, 7, 8, 9"
+    description: "Compile for a specific version of the Java platform. Supported targets: 8, 11, or any higher version listed at https://docs.scala-lang.org/overviews/jdk-compatibility/overview.html"
     abbreviations:
     - "--release"
   - option: "-sourcepath"