Allow mut_from_ref lint in SBase trait

Added #[allow(clippy::mut_from_ref)] to the base() method in the SBase trait to suppress Clippy lint warning. This is necessary due to the method's signature returning a mutable reference from an immutable one, which is required for interoperability with C++ code.

Author: JR-1991

src/traits/sbase.rs

@@ -6,5 +6,6 @@ pub(crate) trait SBase<'a, T>: Inner<'a, T> {
     /// Returns a pinned reference to the underlying SBase object.
     ///
     /// This is useful when you need to pass a pinned reference to C++ code.
+    #[allow(clippy::mut_from_ref)]
     fn base(&self) -> std::pin::Pin<&mut sbmlcxx::SBase>;
 }