refactor: fix clippy warns

I know this is out of the scope of this current PRs, but these minor clippy warnings have been a bit annoying to look at lately, so I've gone ahead and fixed them! :)

src/lune/util/formatting.rs

@@ -231,7 +231,7 @@ pub fn pretty_format_luau_error(e: &LuaError, colorized: bool) -> String {
             let mut found_stack_begin = false;
             for (index, line) in err_lines.clone().iter().enumerate().rev() {
                 if *line == "stack traceback:" {
-                    err_lines[index] = stack_begin.clone();
+                    err_lines[index].clone_from(&stack_begin);
                     found_stack_begin = true;
                     break;
                 }

src/lune/util/traits.rs

@@ -4,6 +4,7 @@ use super::formatting::format_label;
 use crate::RuntimeError;
 
 pub trait LuaEmitErrorExt {
+    #[allow(dead_code)]
     fn emit_error(&self, err: LuaError);
 }
 

src/roblox/instance/terrain.rs

@@ -27,11 +27,13 @@ pub fn add_methods<'lua, M: LuaUserDataMethods<'lua, Instance>>(methods: &mut M)
 }
 
 fn get_or_create_material_colors(instance: &Instance) -> MaterialColors {
-    if let Some(Variant::MaterialColors(material_colors)) = instance.get_property("MaterialColors")
+    if let Variant::MaterialColors(inner) = instance
+        .get_property("MaterialColors")
+        .unwrap_or(Variant::MaterialColors(MaterialColors::default()))
     {
-        material_colors
+        inner
     } else {
-        MaterialColors::default()
+        unreachable!()
     }
 }