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

compiler/testData/diagnostics/tests/annotations/options/assignment.fir.kt

@@ -0,0 +1,10 @@
+@Target(AnnotationTarget.EXPRESSION)
+@Retention(AnnotationRetention.SOURCE)
+annotation class ExprAnn
+
+fun foo(): Int {
+    var a: Int
+    @ExprAnn a = 1
+    @ExprAnn a += 1
+    return a
+}