Fix SwHTMLTextCollOutputInfo::HasParaToken, check for 'p', not 'P'

This had apparently been broken by 73e3aafa99
"convert HTML tags/attributes to lowercase for html export" turning the various
OOO_STRING_SVTOOLS_HTML_... defines from upper- to lowercase, but leaving that
single 'P' alone.  (Though it's unclear whether this makes much of a difference
in practice.  At least none of the `make check` tests apparently change their
behavior due to this.)

Change-Id: I1411b0dd7d82237fccffdff27e4982089a1d64b0
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/180035
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <stephan.bergmann@allotropia.de>

sw/source/filter/html/htmlatr.cxx

@@ -218,7 +218,7 @@ struct SwHTMLTextCollOutputInfo
         bOutDiv( false )
     {}
 
-    bool HasParaToken() const { return aToken.getLength()==1 && aToken[0]=='P'; }
+    bool HasParaToken() const { return aToken == OOO_STRING_SVTOOLS_HTML_parabreak; }
     bool ShouldOutputToken() const { return bOutPara || !HasParaToken(); }
 };