FIR: rename AMBIGUITY to OVERLOAD_RESOLUTION_AMBIGUITY to match FE 1.0

compiler/testData/diagnostics/tests/resolve/invoke/errors/ambiguityForInvoke.fir.kt

@@ -5,7 +5,7 @@ fun Int.invoke(i: Int, a: Any) {}
 fun Int.invoke(a: Any, i: Int) {}
 
 fun foo(i: Int) {
-    <!AMBIGUITY!>i<!>(1, 1)
+    <!OVERLOAD_RESOLUTION_AMBIGUITY!>i<!>(1, 1)
 
-    <!AMBIGUITY!>5<!>(1, 2)
+    <!OVERLOAD_RESOLUTION_AMBIGUITY!>5<!>(1, 2)
 }