[Test] Fix bug with FirCfgDumpHandler which didn't start at all

Flag `alreadyDumped` is needed due to the fact that CFG dumper is not
  prepared to multimodule tests yet, so in such test this handler
  dumps only first module to .dot file.
I forgot to switch it to `true` when it was introduced, so this checker
  actually, didn't handle anything at all

compiler/tests-common-new/tests/org/jetbrains/kotlin/test/frontend/fir/handlers/FirCfgDumpHandler.kt

@@ -25,6 +25,7 @@ class FirCfgDumpHandler(testServices: TestServices) : FirAnalysisHandler(testSer
         if (alreadyDumped || FirDiagnosticsDirectives.DUMP_CFG !in module.directives) return
         val file = info.firFiles.values.first()
         file.accept(FirControlFlowGraphRenderVisitor(builder))
+        alreadyDumped = true
     }
 
     override fun processAfterAllModules(someAssertionWasFailed: Boolean) {