bees: drop the balance/logical workaround that has been disabled for two years

Kernels that needed the balance workaround frankly are too buggy
to run bees at all.  The workaround also makes the locking stories
around logical_ino calls and process exit complicated, so get rid of
it completely.

Signed-off-by: Zygo Blaxell <bees@furryterror.org>

docs/btrfs-kernel.md

@@ -96,16 +96,6 @@ Workarounds for known kernel bugs
   at the same time can lead to a kernel hang.  The workaround is
   to reduce the thread count to 1 with `-c1`.
 
-* **Tree mod log issues**:  bees will detect that a btrfs balance is
-  running, and pause bees activity until the balance is done.  This avoids
-  running both the `LOGICAL_INO` ioctl and btrfs balance at the same time,
-  which avoids kernel crashes on old kernel versions.
-
-  The numbers for "tree mod log issue #" in the above table are arbitrary.
-  There are a lot of them, and they all behave fairly similarly.
-
-  This workaround is less necessary for kernels 5.4.19 and later.
-
 * **Slow backrefs** (aka toxic extents):  Under certain conditions,
   if the number of references to a single shared extent grows too
   high, the kernel consumes more and more CPU while also holding locks