Span with "inline" display mode renders its contents with a wrapping <p> tag

This does not share the same root cause as CONF-44930, and affects instances with and without the collaborative editing feature.

Steps to reproduce:

1. In the editor, the span macro using the { shortcut and add some text to the macro
2. Hit the down arrow key to move to the line below the span macro, and perform step 1 again
3. Check that both macros have the "inline" display option selected (by clicking on the macro placeholder to show the property panel)
4. Click preview

Expected behaviour:

• No line break between the text from both macros
• Macro contents are rendered on separate lines, and the markup appears as follows:

<span id="" class=" conf-macro output-inline" style="" dir="" lang="" title="" data-hasbody="true" data-macro-name="span">
    <p>one</p>
</span>
<span id="" class=" conf-macro output-inline" style="" dir="" lang="" title="" data-hasbody="true" data-macro-name="span">
    <p>two</p>
</span>