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

compiler/testData/diagnostics/tests/operatorRem/remWithModAssign.fir.kt

@@ -0,0 +1,12 @@
+// !LANGUAGE: -ProhibitOperatorMod
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+object RemAndModAssign {
+    operator fun modAssign(x: String) {}
+    operator fun rem(x: Int) = RemAndModAssign
+}
+
+fun test2() {
+    var c = RemAndModAssign
+    c %= 123
+}