Remove unused imports

Author: Zhengyu Gu

substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jfr/JfrEventSupport.java

@@ -29,8 +29,6 @@
 import org.graalvm.compiler.serviceprovider.JavaVersionUtil;
 import org.graalvm.nativeimage.hosted.Feature;
 import org.graalvm.nativeimage.ImageSingletons;
-import org.graalvm.nativeimage.Platform;
-import org.graalvm.nativeimage.Platforms;
 
 import com.oracle.svm.core.annotate.AutomaticFeature;