callbacks: Update PluginRegexp docstring to reference (un)addressedRegexps
callbacks: Update PluginRegexp docstring to reference (un)addressedRegexps

Signed-off-by: James Vega <91ae71a1168cea0b65ac9975da69d5a7753116be@users.sourceforge.net>

mazaclub/mazabot-core,prashantpawar/supybot-rothbot,ProgVal/Limnoria-test,Ban3/Limnoria,kblin/supybot-gsoc,raboof/supybot,haxwithaxe/supybot,buildbot/supybot,jeffmahoney/supybot,mazaclub/mazabot-core,ProgVal/Limnoria-test,Ban3/Limnoria,frumiousbandersnatch/supybot-code