test/coverage.txt: Sort the regression test cases by the issue number.
diff --git a/test/coverage.txt b/test/coverage.txt
index a00f418..4e1dfee 100644
--- a/test/coverage.txt
+++ b/test/coverage.txt
@@ -92,21 +92,21 @@ x [link](/url "foo – bar") x
````````````````````````````````
-### [Issue 15](https://github.com/mity/md4c/issues/15)
+### [Issue 14](https://github.com/mity/md4c/issues/14)
```````````````````````````````` example
-***b* c*
+a***b* c*
.
-<p>*<em><em>b</em> c</em></p>
+<p>a*<em><em>b</em> c</em></p>
````````````````````````````````
-### [Issue 14](https://github.com/mity/md4c/issues/14)
+### [Issue 15](https://github.com/mity/md4c/issues/15)
```````````````````````````````` example
-a***b* c*
+***b* c*
.
-<p>a*<em><em>b</em> c</em></p>
+<p>*<em><em>b</em> c</em></p>
````````````````````````````````