[FIR] Use @file:Suppress("DuplicatedCode") for generated fir impl nodes

Get rid of unwanted warnings in IntelliJ

compiler/fir/tree/tree-generator/src/org/jetbrains/kotlin/fir/tree/generator/printer/builder.kt

@@ -17,6 +17,8 @@ fun Builder.generateCode(generationPath: File): GeneratedFile {
     val stringBuilder = StringBuilder()
     SmartPrinter(stringBuilder).apply {
         printCopyright()
+        println("@file:Suppress(\"DuplicatedCode\")")
+        println()
         println("package $packageName")
         println()
         val imports = collectImports()

compiler/fir/tree/tree-generator/src/org/jetbrains/kotlin/fir/tree/generator/printer/implementation.kt

@@ -19,6 +19,8 @@ fun Implementation.generateCode(generationPath: File): GeneratedFile {
     val stringBuilder = StringBuilder()
     SmartPrinter(stringBuilder).apply {
         printCopyright()
+        println("@file:Suppress(\"DuplicatedCode\")")
+        println()
         println("package $packageName")
         println()
         val imports = collectImports()