chore: Allow unknown clippy lints

same_item_push was added on nightly, but is currently throwing
a false negative. I added an allow for it, but this causes a
warning on stable for an unknown lints, so allow unknown lints for
now.

core/src/lib.rs

@@ -1,4 +1,8 @@
-#![allow(clippy::unneeded_field_pattern, clippy::same_item_push)]
+#![allow(
+    clippy::unneeded_field_pattern,
+    clippy::same_item_push,
+    clippy::unknown_clippy_lints
+)]
 
 #[macro_use]
 mod display_object;

web/src/lib.rs

@@ -1,4 +1,4 @@
-#![allow(clippy::same_item_push)]
+#![allow(clippy::same_item_push, clippy::unknown_clippy_lints)]
 
 //! Ruffle web frontend.
 mod audio;