[LL FIR] rename testdata to testData to avoid copyright generation

We exclude testData pattern from copyright scope

analysis/low-level-api-fir/testData/fileStructure/nestedClassesScript.kts

@@ -0,0 +1,16 @@
+/* RootScriptStructureElement */class A {/* ClassDeclarationStructureElement */
+    class B {/* ClassDeclarationStructureElement */
+        fun x() {/* DeclarationStructureElement */
+        }
+
+        class C {/* ClassDeclarationStructureElement */
+
+        }
+    }
+
+    class E {/* ClassDeclarationStructureElement */
+
+    }
+
+    fun y(): Int = 10/* DeclarationStructureElement */
+}