reflect/protoreflect: remove bool output for Descriptor.Parent method

This is a breaking change.

The equivalent replacement logic is to trivially check whether the
parent descriptor is not nil.

Change-Id: I5c89c1d9f29f9e6f721bbfbcf7774188d8f0086a
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/175987
Reviewed-by: Damien Neil <dneil@google.com>
diff --git a/internal/impl/legacy_test.go b/internal/impl/legacy_test.go
index 583ff33..7fb96ca 100644
--- a/internal/impl/legacy_test.go
+++ b/internal/impl/legacy_test.go
@@ -504,6 +504,8 @@
 						name := v.Type().Method(i).Name
 						if m := v.Method(i); m.Type().NumIn() == 0 && m.Type().NumOut() == 1 {
 							switch name {
+							case "ParentFile", "Parent":
+							// Ignore parents to avoid recursive cycle.
 							case "New":
 								// Ignore New since it a constructor.
 							case "Options":