docs:process:changes: fix version command for btrfs-progs

The command given in the changes.rst document to check the version of
btrfs-progs is:
-> btrfsck
which does not output the version, and according to manual page of the
btrfs-progs the command to check the version of btrfs-progs is:
-> btrfs --version

Add a fix changing the command to check the version of btrfs-progs.

Signed-off-by: Nihar Chaithanya <[email protected]>
Signed-off-by: Jonathan Corbet <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: niharcy

Documentation/process/changes.rst

@@ -46,7 +46,7 @@ jfsutils               1.1.3            fsck.jfs -V
 reiserfsprogs          3.6.3            reiserfsck -V
 xfsprogs               2.6.0            xfs_db -V
 squashfs-tools         4.0              mksquashfs -version
-btrfs-progs            0.18             btrfsck
+btrfs-progs            0.18             btrfs --version
 pcmciautils            004              pccardctl -V
 quota-tools            3.09             quota -V
 PPP                    2.4.0            pppd --version