[FIR-TEST] Add new testdata generated after changes in previous commit

compiler/testData/diagnostics/tests/declarationChecks/valVarFunctionParameter.fir.kt

@@ -0,0 +1,12 @@
+fun f(
+        val a: Int,
+        var b: Int,
+        c: Int,
+        vararg var d: Int,
+        vararg val e: Int,
+        vararg f: Int
+) {
+    
+    
+    a + b + c + d[0] + e[0] + f[0] // to avoid 'unused parameter'
+}