Expect ATX headers in Markdown output

This matches pandoc's new behavior since version 2.11.2.

Author: tarleb

abstract-to-meta/expected.md

@@ -16,8 +16,7 @@ abstract: |
 ---
 
 ::: {.frontmatter}
-Preface
-=======
+# Preface
 
 -   Phasellus purus.
 -   Praesent fermentum tempor tellus.
@@ -26,8 +25,7 @@ Preface
 -   Curabitur lacinia pulvinar nibh.
 :::
 
-Lorem Ipsum
-===========
+# Lorem Ipsum
 
 Quo dolore molestiae et laboriosam occaecati explicabo corrupti. Earum
 expedita ducimus quaerat est quam ut molestiae. Illum deleniti vel

cito/expected.md

@@ -6,14 +6,12 @@ cito_cites:
   - Upper_writers_1974
 ---
 
-Abstract
-========
+# Abstract
 
 This is an example article. It was written under the influence of
 coffee, which acts to counter fatigue [@Li95].
 
-Further reading
-===============
+# Further reading
 
 Authors struggling to fill their document with content are referred to
 @Upper_writers_1974.

scholarly-metadata/expected.md

@@ -32,8 +32,7 @@ institute:
   name: Acme Corporation
 ---
 
-Abstract
-========
+# Abstract
 
 Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod
 tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim

track-changes/expected_accept.markdown

@@ -1,5 +1,4 @@
-Track changes in LaTeX and HTML
-===============================
+# Track changes in LaTeX and HTML
 
 A **simple** comment from me.
 
@@ -19,8 +18,7 @@ And so is this.
 
 One more.
 
-A *header* with a comment {#a-header-width-a-notecomment}
-=========================
+# A *header* with a comment {#a-header-width-a-notecomment}
 
 Some unmodified text ...
 

track-changes/expected_reject.markdown

@@ -1,5 +1,4 @@
-Track changes in LaTeX and HTML
-===============================
+# Track changes in LaTeX and HTML
 
 A **simple** comment from me.
 
@@ -19,8 +18,7 @@ And so is this.
 
 One more.
 
-A *header* width  comment {#a-header-width-a-notecomment}
-========================
+# A *header* width  comment {#a-header-width-a-notecomment}
 
 Some unmodified text ...