selftests: mlxsw: qos_pfc: Remove wrong description

In the diagram of the topology, $swp3 and $swp4 are described as 1Gbps
ports. This is wrong information, the test does not configure such speed.

Cc: Shuah Khan <shuah@kernel.org>
Fixes: bfa8047 ("selftests: mlxsw: Add a PFC test")
Signed-off-by: Amit Cohen <amcohen@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Petr Machata <petrm@nvidia.com>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Link: https://lore.kernel.org/r/0087e2d416aff7e444d15f7c2958fc1d438dc27e.1705502064.git.petrm@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: Amit Cohen

tools/testing/selftests/drivers/net/mlxsw/qos_pfc.sh

@@ -40,7 +40,6 @@
 # |   + $swp1          $swp3 +                    + $swp4                     |
 # |   | iPOOL1        iPOOL0 |                    | iPOOL2                    |
 # |   | ePOOL4        ePOOL5 |                    | ePOOL4                    |
-# |   |                1Gbps |                    | 1Gbps                     |
 # |   |        PFC:enabled=1 |                    | PFC:enabled=1             |
 # | +-|----------------------|-+                +-|------------------------+  |
 # | | + $swp1.111  $swp3.111 + |                | + $swp4.111              |  |