repo.py: remove alternates-reading branch from git_essential_directories()

Reference clones are being removed from 2.5 entirely, so
objects/info/alternates will never exist and this branch is permanently
dead. The now-unused suppress import goes with it.

Jira: CMK-33523
Change-Id: Id9b0deee14f202d27e02b7fcba250750851ec5ee

Author: Synss

tests/testlib/common/repo.py

@@ -14,7 +14,6 @@
 import subprocess
 import sys
 from collections.abc import Callable
-from contextlib import suppress
 from functools import cache
 from pathlib import Path
 
@@ -168,15 +167,6 @@ def git_essential_directories(checkout_dir: Path) -> list[str]:
     if not common_dir.is_relative_to(checkout_dir):
         essential_dirs.append(common_dir.as_posix())
 
-    # In case of reference clones we also need to access them.
-    # Not sure if 'objects/info/alternates' can contain more than one line and if we really need
-    # the parent, but at least this one is working for us
-    with suppress(FileNotFoundError):
-        with (common_dir / "objects/info/alternates").open() as alternates:
-            for alternate in (Path(line).parent for line in alternates):
-                if not alternate.is_relative_to(checkout_dir):
-                    essential_dirs.append(alternate.as_posix())
-
     return essential_dirs