Documentation/gitformat-pack.txt: drop mixed version section

This section was added in 3d89a8c (Documentation/technical: add
cruft-packs.txt, 2022-05-20) to highlight a potential pitfall when
deploying cruft packs in an environment where multiple versions of Git
are GC-ing the same repository.

Now that it has been more than a year since 3d89a8c was written,
let's drop this section as it is no longer relevant.

Signed-off-by: Taylor Blau <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: ttaylorr

Documentation/gitformat-pack.txt

@@ -588,32 +588,6 @@ later on.
 It is linkgit:git-gc[1] that is typically responsible for removing expired
 unreachable objects.
 
-=== Caution for mixed-version environments
-
-Repositories that have cruft packs in them will continue to work with any older
-version of Git. Note, however, that previous versions of Git which do not
-understand the `.mtimes` file will use the cruft pack's mtime as the mtime for
-all of the objects in it. In other words, do not expect older (pre-cruft pack)
-versions of Git to interpret or even read the contents of the `.mtimes` file.
-
-Note that having mixed versions of Git GC-ing the same repository can lead to
-unreachable objects never being completely pruned. This can happen under the
-following circumstances:
-
-  - An older version of Git running GC explodes the contents of an existing
-    cruft pack loose, using the cruft pack's mtime.
-  - A newer version running GC collects those loose objects into a cruft pack,
-    where the .mtime file reflects the loose object's actual mtimes, but the
-    cruft pack mtime is "now".
-
-Repeating this process will lead to unreachable objects not getting pruned as a
-result of repeatedly resetting the objects' mtimes to the present time.
-
-If you are GC-ing repositories in a mixed version environment, consider omitting
-the `--cruft` option when using linkgit:git-repack[1] and linkgit:git-gc[1], and
-setting the `gc.cruftPacks` configuration to "false" until all writers
-understand cruft packs.
-
 === Alternatives
 
 Notable alternatives to this design include: