Switch default JVM target to 1.8

#KT-29405 Fixed

compiler/testData/diagnostics/tests/targetedBuiltIns/stream.fir.kt

@@ -1,13 +0,0 @@
-// !WITH_NEW_INFERENCE
-// FULL_JDK
-
-import java.util.stream.*
-
-interface A : Collection<String> {
-    override fun stream(): Stream<String> = Stream.of()
-}
-
-fun foo(x: List<String>, y: A) {
-    x.stream().filter { it.length > 0 }.collect(Collectors.toList())
-    y.stream().filter { it.length > 0 }
-}

compiler/testData/diagnostics/tests/targetedBuiltIns/stream.kt

@@ -1,10 +1,10 @@
-// !WITH_NEW_INFERENCE
+// FIR_IDENTICAL
 // FULL_JDK
 
 import java.util.stream.*
 
 interface A : Collection<String> {
-    override fun stream(): Stream<String> = Stream.<!INTERFACE_STATIC_METHOD_CALL_FROM_JAVA6_TARGET_ERROR!>of<!>()
+    override fun stream(): Stream<String> = Stream.of()
 }
 
 fun foo(x: List<String>, y: A) {