The stray <span> was added by Gabriel Wicke in r2953 "to allow better css styling", but doesn't appear to have been really used. Doesn't seem any clear benefit to it, and it causes problems with fancy media types like OggHandler, so let's kill it and fix the tests. :)
!! input
[[Image:foobar.jpg|right]]
!! result
!! input
[[Image:foobar.jpg|right]]
!! result
-<div class="floatright"><span><a href="/wiki/Image:Foobar.jpg" class="image" title="Foobar.jpg"><img alt="" src="http://example.com/images/3/3a/Foobar.jpg" width="1941" height="220" border="0" /></a></span></div>
+<div class="floatright"><a href="/wiki/Image:Foobar.jpg" class="image" title="Foobar.jpg"><img alt="" src="http://example.com/images/3/3a/Foobar.jpg" width="1941" height="220" border="0" /></a></div>
!! input
[[Image:foobar.jpg|right|Caption text]]
!! result
!! input
[[Image:foobar.jpg|right|Caption text]]
!! result
-<div class="floatright"><span><a href="/wiki/Image:Foobar.jpg" class="image" title="Caption text"><img alt="Caption text" src="http://example.com/images/3/3a/Foobar.jpg" width="1941" height="220" border="0" /></a></span></div>
+<div class="floatright"><a href="/wiki/Image:Foobar.jpg" class="image" title="Caption text"><img alt="Caption text" src="http://example.com/images/3/3a/Foobar.jpg" width="1941" height="220" border="0" /></a></div>
!! input
[[Image:foobar.jpg|centre]]
!! result
!! input
[[Image:foobar.jpg|centre]]
!! result
-<div class="center"><div class="floatnone"><span><a href="/wiki/Image:Foobar.jpg" class="image" title="Foobar.jpg"><img alt="" src="http://example.com/images/3/3a/Foobar.jpg" width="1941" height="220" border="0" /></a></span></div></div>
+<div class="center"><div class="floatnone"><a href="/wiki/Image:Foobar.jpg" class="image" title="Foobar.jpg"><img alt="" src="http://example.com/images/3/3a/Foobar.jpg" width="1941" height="220" border="0" /></a></div></div>
!! input
[[Image:foobar.jpg|none]]
!! result
!! input
[[Image:foobar.jpg|none]]
!! result
-<div class="floatnone"><span><a href="/wiki/Image:Foobar.jpg" class="image" title="Foobar.jpg"><img alt="" src="http://example.com/images/3/3a/Foobar.jpg" width="1941" height="220" border="0" /></a></span></div>
+<div class="floatnone"><a href="/wiki/Image:Foobar.jpg" class="image" title="Foobar.jpg"><img alt="" src="http://example.com/images/3/3a/Foobar.jpg" width="1941" height="220" border="0" /></a></div>