No longer use a SecurityManager during internal testing (#4078)

On some JDK versions, using a security manager crashes the JVM
because the Kotlin runtime can't load. Since the security manager
API is deprecated anyway and the security manager didn't test
anything extremely important, we just remove it.

Author: dkhalanskyjb

kotlinx-coroutines-core/build.gradle.kts

@@ -164,13 +164,6 @@ val jvmTest by tasks.getting(Test::class) {
     minHeapSize = "1g"
     maxHeapSize = "1g"
     enableAssertions = true
-    if (!Idea.active) {
-        // We should not set this security manager when `jvmTest`
-        // is invoked by IntelliJ IDEA since we need to pass
-        // system properties for Lincheck and stress tests.
-        // TODO Remove once IDEA is smart enough to select between `jvmTest`/`jvmStressTest`/`jvmLincheckTest` #KTIJ-599
-        systemProperty("java.security.manager", "kotlinx.coroutines.TestSecurityManager")
-    }
     // 'stress' is required to be able to run all subpackage tests like ":jvmTests --tests "*channels*" -Pstress=true"
     if (!Idea.active && rootProject.properties["stress"] == null) {
         exclude("**/*LincheckTest*")