Fix import of grounded_op! macro

Co-authored-by: luketpeterson <[email protected]>

lib/src/metta/runner/stdlib.rs

@@ -32,7 +32,7 @@ macro_rules! grounded_op {
             }
         }
 
-        impl Display for $name {
+        impl std::fmt::Display for $name {
             fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
                 write!(f, $disp)
             }