Revert "LaTeX: Use \ul (from the "soul" package) instead of \uline"

This reverts commit b399ff0cba2382bf52d5bb6ef2b4a776fe0ac902.

lisp/org.el

@@ -3843,7 +3843,6 @@ header, or they will be appended."
     (""     "wrapfig"   nil)
     (""     "rotating"  nil)
     ("normalem" "ulem"  t)
-    (""     "soul"      t)
     (""     "amsmath"   t)
     (""     "textcomp"  t)
     (""     "marvosym"  t)

lisp/ox-latex.el

@@ -533,7 +533,7 @@ When nil, no transformation is made."
 					 (code . verb)
 					 (italic . "\\emph{%s}")
 					 (strike-through . "\\sout{%s}")
-					 (underline . "\\ul{%s}")
+					 (underline . "\\uline{%s}")
 					 (verbatim . protectedtexttt))
   "Alist of LaTeX expressions to convert text markup.