Remove directives that have no effect from bytecode text tests

All bytecode text tests are run with stdlib in the classpath and only
for JVM backend, therefore directives WITH_RUNTIME, TARGET_BACKEND,
IGNORE_BACKEND are not needed

compiler/testData/codegen/bytecodeText/when/kt18818.kt

@@ -1,5 +1,3 @@
-// WITH_RUNTIME
-
 fun findUserId(username: String): Long? = null
 
 fun main(args: Array<String>) {
@@ -11,4 +9,4 @@ fun main(args: Array<String>) {
     }
 }
 
-// 0 areEqual
+// 0 areEqual