LaTeX writer: protect \phantomsection (#10688)

`\phantomsection` is used for anchors. When these occur inside a caption,
a LaTeX error is raised unless the `\phantomsection` is protected using `\protect`.
So we now `\protect` every `\phantomsection` (even outside of captions -- this
seems to be harmless).

Author: etclub

src/Text/Pandoc/Writers/LaTeX/Util.hs

@@ -267,7 +267,7 @@ hypertarget ident = do
       return $ text "\\protect\\hypertarget" <> braces ref <> "{}"
      else do
       label <- labelFor ident
-      return $ text "\\phantomsection" <> label
+      return $ text "\\protect\\phantomsection" <> label
 
 labelFor :: PandocMonad m => Text -> LW m (Doc Text)
 labelFor ""    = return empty