Delay UNUSED_PARAMETER on main parameter until 1.4 (part of KT-26999)

compiler/testData/diagnostics/testsWithStdLib/CallToMainRedeclaredInMultiFile.kt

@@ -1,8 +1,8 @@
 // FILE: a.kt
-fun main(<!UNUSED_PARAMETER!>args<!>: Array<String>) {}
+fun main(args: Array<String>) {}
 
 // FILE: b.kt
-fun main(<!UNUSED_PARAMETER!>args<!>: Array<String>) {}
+fun main(args: Array<String>) {}
 
 // FILE: c.kt
 fun foo() { <!OVERLOAD_RESOLUTION_AMBIGUITY!>main<!>(arrayOf("a", "b")) }