WYSWIYG: Fixed misaligned table cell p line height

Removes an editor-specific line-height which was overriding cell
paragraph line height, causing mis-aligned style compared to viewing.
Checked a range of styles and looked at history, could not see original
purpose of the line-height removed here.
Closes #4960

resources/sass/_tinymce.scss

@@ -46,11 +46,6 @@
   display: block;
 }
 
-// In editor line height override
-.page-content.mce-content-body p {
-  line-height: 1.6;
-}
-
 // Pad out bottom of editor
 body.page-content.mce-content-body  {
   padding-bottom: 5rem;