rust: don't escape spaces in regex
Spaces are not in fact a regex special character, and escaping them is
not correct.
{header}
<id>{urlbase}{url|urlescape}atom-log/tip/{file|escape}</id>
<link rel="self" href="{urlbase}{url|urlescape}atom-log/tip/{file|urlescape}"/>
<title>{repo|escape}: {file|escape} history</title>
{latestentry%feedupdated}
{entries%changelogentry}
</feed>