[K/N]: Do not require JDK11 for :native:native.tests

This commit provides a small fix in the code of a native test runner so that JDK11 is not required and removes the JDK11 target for the atomicfu-compiler-plugin.

Fixes KT-61293

Merge-request: KT-MR-11757
Merged-by: Maria Sokolova <maria.sokolova@jetbrains.com>

native/native.tests/tests/org/jetbrains/kotlin/konan/blackboxtest/support/runner/AbstractLocalProcessRunner.kt

@@ -154,8 +154,8 @@ private class UnfilteredProcessOutput {
     private val stdErr = ByteArrayOutputStream()
 
     fun toProcessOutput(outputFilter: TestOutputFilter): ProcessOutput = ProcessOutput(
-        stdOut = outputFilter.filter(stdOut.toString(Charsets.UTF_8)),
-        stdErr = stdErr.toString(Charsets.UTF_8)
+        stdOut = outputFilter.filter(stdOut.toString(Charsets.UTF_8.name())),
+        stdErr = stdErr.toString(Charsets.UTF_8.name())
     )
 
     companion object {