The simple way to do this is to use the translate()
function, which can be used to replace certain characters with other characters, or with nothing. It looks like this is the line that outputs the value you want to fix up:
<xsl:value-of select="normalize-space($topicTitle)"/>
So you could simply modify this to:
<xsl:value-of select="translate(normalize-space($topicTitle), '­', '')"/>
to remove all the soft hyphens. If you would like to replace them with spaces or ordinary hyphens, you could do either of the following, respectively:
<xsl:value-of select="translate(normalize-space($topicTitle), '­', ' ')"/>
<xsl:value-of select="translate(normalize-space($topicTitle), '­', '-')"/>