chore(styles): Revert an erroneously changed line in styles

Introduced when implementing "Better support null in YAML style files"
Noted here as a "chore" as this was just a few days ago and we haven't
tagged a release yet, but this is a bug fix.

packages/resilient/styles/init.lua

@@ -484,7 +484,7 @@ function package:registerCommands ()
         vglue = cloneStyleSkip(vglue, name)
         -- Not sure here whether it should be an explicit glue or not,
         -- but it seems so to me...
-        SILE.typesetter:pushExplicitVglue(vglue)
+        SILE.typesetter:pushVglue(vglue)
       end
       if novbreak then SILE.call("novbreak") end
     end