Fix for Warning on Check

an additional `:render` was wrongly placed and has been removed, travi build should work now and the build check worked on my end as well.
diff --git a/R/posterdown_latex.R b/R/posterdown_latex.R
index 0ba4da7..d56e6a1 100644
--- a/R/posterdown_latex.R
+++ b/R/posterdown_latex.R
@@ -4,7 +4,7 @@
 #' @param ... Additional arguments to `rmarkdown::pdf_document`
 #'
 #' @return R Markdown output format to pass to
-#'   [rmarkdown:render::render()]
+#'   [rmarkdown::render()]
 #'
 #' @examples
 #'