hgweb: use css margin instead of empty <p> before diffstat table The <p> elements were used to create an empty space between the diffstat link and the diffstat table, but they don't have any semantic meaning, so it is better to use css instead. Default margins for <p> elements can differ depending on the browser, but usually the margin is 1em (exceptions are IE 6 and 7 with 14pt, which is comparable). The css rule sets top margin to 1em. This change is a "better version" of 70cfa7e1611b, where <p> elements were simply properly closed.