fix: remove git-cliff unreleased markers from changelogs (#1789)

Removes the unnecessary `git-cliff-unreleased` lines (which shouldn't be
rendered anyway, as they are intended to be HTML comments).

Author: barjin

apify-docs-theme/src/markdown.js

@@ -20,7 +20,7 @@ const incrementHeadingLevels = () => (tree) => {
 
 const removeGitCliffMarkers = () => (tree) => {
     visitParents(tree, 'html', (node) => {
-        const gitCliffMarkerRegex = /generated by git-cliff/ig;
+        const gitCliffMarkerRegex = /generated by git-cliff|git-cliff-unreleased/ig;
         const match = gitCliffMarkerRegex.exec(node.value);
 
         if (match) node.value = '';