fix centering when using threeparttable

When threeparttable=T and a caption is set the table is not being centered on page. In order for the table to be centered on the page, \centering needs to be before \begin{threeparttable}.  Right now, \centering is being put after \caption and the deleted lines insert \begin{threeparttable} between the two.  By removing those lines, \being{threeparttable} is inserted after centering, but before \begin{tabular}.  This results in the table being centered on page.
diff --git a/R/footnote.R b/R/footnote.R
index 066e96f..d67382b 100644
--- a/R/footnote.R
+++ b/R/footnote.R
@@ -204,15 +204,10 @@
   footnote_text <- latex_tfoot_maker(footnote_table, footnote_as_chunk,
                                      table_info$ncol, threeparttable)
   if (threeparttable) {
-    if (grepl("\\\\caption\\{.*?\\}", out)) {
-      out <- sub("\\\\caption\\{", "\\\\begin{threeparttable}\n\\\\caption{",
-                 out)
-    } else {
       out <- sub(paste0("\\\\begin\\{", table_info$tabular, "\\}"),
                  paste0("\\\\begin{threeparttable}\n\\\\begin{",
                         table_info$tabular, "}"),
                  out)
-    }
     out <- sub(table_info$end_tabular,
                paste0("\\\\end{", table_info$tabular,
                       "}\n\\\\begin{tablenotes}",