Move objects to a lower exit class.

Paragraph's exit matcher which detects elements was causing the plain list parser to exit after the first item was parsed which was causing significant amounts of re-parsing.

src/parser/subscript_and_superscript.rs

@@ -162,7 +162,7 @@ fn script_with_braces<'r, 's>(
             },
         ))
         .with_additional_node(ContextElement::ExitMatcherNode(ExitMatcherNode {
-            class: ExitClass::Beta,
+            class: ExitClass::Gamma,
             exit_matcher: &script_with_braces_end,
         }));