Fix precedence parsing of parens. Limit use (#1606)

crates/nu-protocol/src/syntax_shape.rs

@@ -30,8 +30,6 @@ pub enum SyntaxShape {
     Unit,
     /// An operator
     Operator,
-    /// A parenthesized math expression, eg `(1 + 3)`
-    Parenthesized,
     /// A math expression, eg `foo > 1`
     Math,
 }
@@ -53,7 +51,6 @@ impl PrettyDebug for SyntaxShape {
             SyntaxShape::Table => "table",
             SyntaxShape::Unit => "unit",
             SyntaxShape::Operator => "operator",
-            SyntaxShape::Parenthesized => "math with parentheses",
             SyntaxShape::Math => "condition",
         })
     }