Meta: Fix Markdown linting

The new help:https://man links were linted incorrectly, and they're now
skipped by the markdown linter, such as in the pre-commit hook

Userland/Utilities/markdown-check.cpp

@@ -16,6 +16,7 @@
 #include <AK/HashTable.h>
 #include <AK/LexicalPath.h>
 #include <AK/OwnPtr.h>
+#include <AK/RecursionDecision.h>
 #include <AK/StdLibExtras.h>
 #include <AK/Vector.h>
 #include <LibCore/File.h>
@@ -25,18 +26,6 @@
 static bool is_missing_file_acceptable(String const& filename)
 {
  const StringView acceptable_missing_files[] = {
- // FIXME: Please write these manpages!
- "/usr/share/man/man2/accept.md",
- "/usr/share/man/man2/exec.md",
- "/usr/share/man/man2/fcntl.md",
- "/usr/share/man/man2/fork.md",
- "/usr/share/man/man2/ioctl.md",
- "/usr/share/man/man2/listen.md",
- "/usr/share/man/man2/mmap.md",
- "/usr/share/man/man2/mprotect.md",
- "/usr/share/man/man2/open.md",
- "/usr/share/man/man2/ptrace.md",
- "/usr/share/man/man5/perfcore.md",
  // These ones are okay:
  "/home/anon/js-tests/test-common.js",
  "/man1/index.html",
@@ -167,6 +156,11 @@ RecursionDecision MarkdownLinkage::visit(Markdown::Text::LinkNode const& link_no
  outln("Not checking external link {}", href);
  return RecursionDecision::Recurse;
  }
+ if (href.starts_with("help:https://")) {
+ // TODO: Check that the man page actually exists. (That check would also fail because we are currently referring to some nonexistent man pages.)
+ outln("Not checking man page link {}", href);
+ return RecursionDecision::Recurse;
+ }
  if (href.starts_with("file:https://")) {
  // TODO: Resolve relative to $SERENITY_SOURCE_DIR/Base/
  // Currently, this affects only one link, so it's not worth the effort.