Revert "docs: Fix grammar in borg mount docs #8510"

This reverts commit d3f3082bf4714fd394b045273b3d42034868c6c5.

Comment by jdchristensen:

I agree that "wipe clean" is correct grammar, but it doesn't match the situation in "unmount cleanly".
The change in this patch is definitely wrong.
Putting it another way, one would never say that we "clean unmount a filesystem".
We say that we "cleanly unmount a filesystem", or in other words, that it "unmounts cleanly".

But the original text is slightly awkward, so I would propose: "When running in the foreground,
^C/SIGINT cleanly unmounts the filesystem, but other signals or crashes do not."

(Not that this guarantees anything, but I'm a native speaker.)

src/borg/archiver/mount_cmds.py

@@ -120,7 +120,7 @@ class MountMixIn:
         Unmounting in these cases could cause an active rsync or similar process
         to delete data unintentionally.
 
-        When running in the foreground ^C/SIGINT unmounts clean, but other
+        When running in the foreground ^C/SIGINT unmounts cleanly, but other
         signals or crashes do not.
         """
         )