coverbrowser: fix some vertical alignments (#3779)

introduced by the recent correction to UnderlineContainer.

plugins/coverbrowser.koplugin/listmenu.lua

@@ -160,13 +160,13 @@ function ListMenuItem:init()
     -- even with classic menu)
     self.underline_h = 1 -- smaller than default (3) to not shift our vertical aligment
     self._underline_container = UnderlineContainer:new{
-        vertical_align = "center",
+        vertical_align = "top",
+        padding = 0,
         dimen = Geom:new{
             w = self.width,
             h = self.height
         },
         linesize = self.underline_h,
-        padding = 0,
         -- widget : will be filled in self:update()
     }
     self[1] = self._underline_container

plugins/coverbrowser.koplugin/mosaicmenu.lua

@@ -348,7 +348,8 @@ function MosaicMenuItem:init()
     -- even with classic menu)
     self.underline_h = 1 -- smaller than default (3), don't waste space
     self._underline_container = UnderlineContainer:new{
-        vertical_align = "center",
+        vertical_align = "top",
+        padding = 0,
         dimen = Geom:new{
             w = self.width,
             h = self.height