Add Kotlin version bump to breaking changes (#987)

docs/modules/release-notes/pages/0.28.adoc

@@ -256,6 +256,10 @@ foo { ...bar...baz } // Syntax error
 
 The minimum Gradle version for the xref:main:pkl-gradle:index.adoc[Gradle Plugin] has been bumped to 8.2 (https://github.com/apple/pkl/pull/901[#901]).
 
+=== Minimum Kotlin version bump
+
+For users of Pkl's Kotlin libraries, the minimum Kotlin version has been bumped to 2.0 (https://github.com/apple/pkl/pull/900[#900]).
+
 === Java/Kotlin API breaking changes
 
 Breaking changes have been made to the Java/Kotlin APIs (https://github.com/apple/pkl/pull/748[#748], https://github.com/apple/pkl/pull/749[#749], https://github.com/apple/pkl/pull/776[#776], https://github.com/apple/pkl/pull/793[#793], https://github.com/apple/pkl/pull/808[#808], https://github.com/apple/pkl/pull/810[#810]).
@@ -337,7 +341,6 @@ For users that use both Pkl and other Truffle languages, this means that their v
 * Documentation improvements (https://github.com/apple/pkl/pull/792[#792], https://github.com/apple/pkl/pull/846[#846], https://github.com/apple/pkl/pull/860[#860], https://github.com/apple/pkl/pull/892[#892], https://github.com/apple/pkl/pull/921[#921], https://github.com/apple/pkl/pull/937[#937], https://github.com/apple/pkl/pull/943[#943], https://github.com/apple/pkl/pull/944[#944], https://github.com/apple/pkl/pull/955[#955], https://github.com/apple/pkl/pull/956[#956], https://github.com/apple/pkl/pull/973[#973]).
 * The repository now requires Java 21 or higher to build (https://github.com/apple/pkl/pull/876[#876]).
 * Enable multi-jdk testing via `-DmultiJdkTesting=true` flag when building Pkl (https://github.com/apple/pkl/pull/876[#876]).
-* Pkl's version of Kotlin has been upgraded to 2.0 (https://github.com/apple/pkl/pull/900[#900]).
 * Allow setting commit id via `-DcommitId` flag when building Pkl (https://github.com/apple/pkl/pull/954[#954]).
 
 == Bugs fixed [small]#🐜#