Fix the number of params on CSLReferences

This is to fix a [compilation error](jgm/pandoc#7215) with the newer pandoc

Author: BlackEdder

inst/rmarkdown/templates/elsevier/resources/template.tex

@@ -139,7 +139,7 @@
   \everypar{\setlength{\hangindent}{\cslhangindent}}\ignorespaces$endif$}%
   {\par}
 % For Pandoc 2.11+
-\newenvironment{CSLReferences}[3] % #1 hanging-ident, #2 entry spacing
+\newenvironment{CSLReferences}[2] % #1 hanging-ident, #2 entry spacing
  {% don't indent paragraphs
   \setlength{\parindent}{0pt}
   % turn on hanging indent if param 1 is 1