Adjusted *.asRichtextEmbed.ftl templates

With CMS-19278 closing and opening <p> tags have been added to CMTeasable.asRichtextEmbed.ftl to avoid breaking HTML validity. Since embedded content can also be embedded inside headlines, tables, etc., this change actually broke HTML validity even more. This change also caused empty <p> tags surrounding embedded content, especially when embedded content was placed at the beginning of the richtext. Now these additional closing and re-opening <p> tags have been removed in all *.asRichtextEmbed.ftl templates.

(CMS-24147)