Switch from pretty-simple to pretty-show for native output.

Update tests.

Reason:  it turns out that the native output generated by
pretty-simple isn't always readable by the native reader.
According to https://github.com/cdepillabout/pretty-simple/issues/99
it is not a design goal of the library that the rendered values
be readable using 'read'.  This makes it unsuitable for our
purposes.

pretty-show is a bit slower and it uses 4-space indents
(non-configurable), but it doesn't have this serious drawback.

1 files changed, 32 insertions, 33 deletions

diff --git a/test/command/5700.md b/test/command/5700.md
index ca8ab19fd..eae3663e5 100644
--- a/test/command/5700.md
+++ b/test/command/5700.md
@@ -2,39 +2,38 @@
 % pandoc -t native -s --metadata-file command/5700-metadata-file-1.yml --metadata-file command/5700-metadata-file-2.yml
 ^D
 Pandoc
-  ( Meta
-    { unMeta = fromList
-      [
-        ( "desc"
-        , MetaInlines
-          [ Str "Both"
-          , Space
-          , Str "of"
-          , Space
-          , Str "these"
-          , Space
-          , Str "files"
-          , Space
-          , Str "should"
-          , Space
-          , Str "be"
-          , Space
-          , Str "loaded."
+  Meta
+    { unMeta =
+        fromList
+          [ ( "desc"
+            , MetaInlines
+                [ Str "Both"
+                , Space
+                , Str "of"
+                , Space
+                , Str "these"
+                , Space
+                , Str "files"
+                , Space
+                , Str "should"
+                , Space
+                , Str "be"
+                , Space
+                , Str "loaded."
+                ]
+            )
+          , ( "title"
+            , MetaInlines
+                [ Str "Multiple"
+                , Space
+                , Str "metadata"
+                , Space
+                , Str "files"
+                , Space
+                , Str "test"
+                ]
+            )
           ]
-        )
-      ,
-        ( "title"
-        , MetaInlines
-          [ Str "Multiple"
-          , Space
-          , Str "metadata"
-          , Space
-          , Str "files"
-          , Space
-          , Str "test"
-          ]
-        )
-      ]
     }
-  ) []
+  []
 ```