fixed some spacing issues

src/sequence.typ

@@ -40,6 +40,8 @@
 #let render(pars-i, x-pos, participants, elmt, y, lifelines) = {
   let shapes = ()
 
+  y -= Y-SPACE
+
   // Reserve space for comment
   if elmt.comment != none {
     y -= measure(box(elmt.comment)).height / 1pt + 6
@@ -185,7 +187,6 @@
     dst-line.lines.push(("create", y))
     lifelines.at(i2) = dst-line
   }
-  y -= Y-SPACE
 
   let r = (y, lifelines, shapes)
   return r