Remove JVM_OLD-specific test data from backend diagnostic tests

Old JVM backend is only used as a fallback in Evaluate Expression in the
IDE at this point, so it's supposed to compile only correct code anyway.

compiler/testData/diagnostics/testsWithJvmBackend/duplicateJvmSignature/functionAndProperty/trait_old.kt

@@ -1,7 +0,0 @@
-// TARGET_BACKEND: JVM_OLD
-
-interface T {
-    val x: Int
-        <!CONFLICTING_JVM_DECLARATIONS, CONFLICTING_JVM_DECLARATIONS!>get()<!> = 1
-    <!CONFLICTING_JVM_DECLARATIONS, CONFLICTING_JVM_DECLARATIONS!>fun getX()<!> = 1
-}

compiler/testData/diagnostics/testsWithJvmBackend/duplicateJvmSignature/functionAndProperty/trait_old.txt

@@ -1,9 +0,0 @@
-package
-
-public interface T {
-    public open val x: kotlin.Int
-    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
-    public open fun getX(): kotlin.Int
-    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
-    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
-}