Remove leftovers of platformName and platformStatic in test data

Drop unnecessary imports, rename some tests

compiler/testData/diagnostics/testsWithStdLib/duplicateJvmSignature/jvmStaticInClassObject.kt

@@ -1,5 +1,3 @@
-import kotlin.jvm.JvmStatic
-
 open class Base {
     fun foo() {}
 }

compiler/testData/diagnostics/testsWithStdLib/duplicateJvmSignature/jvmStaticInObject.kt

@@ -1,6 +1,4 @@
 // !DIAGNOSTICS: -UNUSED_PARAMETER
-import kotlin.jvm.JvmStatic
-
 open class Base {
     fun `foo$default`(i: Int, mask: Int, mh: Any) {}
 }