Remove get_local function from Vm

It does not use the global/local dichotomy and it wasn't being used

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

src/vm/mod.rs

@@ -340,10 +340,4 @@ impl<'c> Vm<'c> {
         let locals = frame.locals_mut();
         locals.insert(name.index(), value);
     }
-
-    fn get_local(&mut self, name: Name) -> Option<ObjRef> {
-        self.frame()
-            .and_then(|frame| frame.locals().get(&name.index()))
-            .cloned()
-    }
 }