Fix lesser block exit priority.

The paragraph end was matching text inside lesser blocks.

src/parser/lesser_block.rs

@@ -200,7 +200,7 @@ pub fn src_block<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s st
         .with_additional_node(ContextElement::ConsumeTrailingWhitespace(true))
         .with_additional_node(ContextElement::Context("lesser block"))
         .with_additional_node(ContextElement::ExitMatcherNode(ExitMatcherNode {
-            class: ExitClass::Beta,
+            class: ExitClass::Alpha,
             exit_matcher: &lesser_block_end_specialized,
         }));
     let parameters = match parameters {