Bump org.jetbrains.kotlin:kotlin-gradle-plugin-api from 1.9.20 to 1.9.21 in /devtools/gradle #377

Job	Run time
Attach pull request number	2s
CI Sanity Check	31s
Initial JDK 11 Build	12m 34s
Calculate Test Jobs	9s
Gradle Tests - JDK 11	28m 30s
Devtools Tests - JDK ${{ matrix.java.name }}	0s
Kubernetes Tests - JDK ${{ matrix.java.name }}	0s
Gradle Tests - JDK 11 Windows	53m 10s
JVM Tests - JDK 11	7m 12s
JVM Tests - JDK 17	6m 22s
Maven Tests - JDK ${{ matrix.java.name }}	0s
JVM Tests - JDK 21	6m 21s
Quickstarts Compilation - JDK 17	5m 15s
Native Tests - Misc4	17m 2s
JVM Tests - JDK 17 Windows	9m 1s
MicroProfile TCKs Tests	0s
Native Tests - Virtual Thread - ${{ matrix.category }}	0s
Build report	19s
	2h 26m 28s

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