[FIR JS] Fix current tests

compiler/testData/ir/irJsText/dynamic/dynamicArrayAssignment.fir.kt.txt

@@ -0,0 +1,8 @@
+fun testArrayAssignment(d: dynamic) {
+  d["KEY"] = 1 /*~> Unit */
+}
+
+fun testArrayAssignmentFake(d: dynamic) {
+  d.set("KEY", 2) /*~> Unit */
+}
+