[osis-core] Remove ":" from the grain part of osisRef

[Todd Tillinghast]

>From the osisRegexTest.xml posted earlier today:

<p osisRef="Matt.1.1@cp:[65]">Matt.1.1@cp:[65]</p> 
<p osisRef="Matt.1.1@s:[Messiah]">Matt.1.1@s:[Messiah]</p>

The ":" is not needed because the "[...]" is already required after "cp"
and "s".

Todd