Fix precedence of absolute value operation

As the absolute value operation has its own type of parentheses, it
never needs to take precedence over other terms in order to be displayed
correctly. To avoid extraneous parentheses around absolute value
operations, set its precedence level to 0.

src/format.rs

@@ -15,6 +15,8 @@ impl Precedence for crate::Term
 			| Self::Integer(_)
 			| Self::String(_)
 			| Self::Variable(_)
+			| Self::UnaryOperation(
+				crate::UnaryOperation{operator: crate::UnaryOperator::AbsoluteValue, ..})
 				=> 0,
 			Self::UnaryOperation(
 				crate::UnaryOperation{operator: crate::UnaryOperator::Negative, ..})
@@ -33,9 +35,6 @@ impl Precedence for crate::Term
 			| Self::BinaryOperation(
 				crate::BinaryOperation{operator: crate::BinaryOperator::Subtract, ..})
 				=> 4,
-			Self::UnaryOperation(
-				crate::UnaryOperation{operator: crate::UnaryOperator::AbsoluteValue, ..})
-				=> 5,
 		}
 	}
 }