[consutil][show] Remove root need from show line command

[Blueve]

- What I did

Remove root privilege need for consutil show and show line command.

As discuss in this thread (sonic-net/sonic-buildimage#5438), I am going to remove unnecessary root privilege need from console commands.

- How I did it

• Simply remove the check
• Add unit test for consutil show command
• Fix a known typo (found by adding unittest)

- How to verify it

Build py-wheel package and install+test on a physical SONiC DUT

- Previous command output (if the output of a command-line utility has changed)

admin@sonic:~$ show line
Root privileges are required for this operation

- New command output (if the output of a command-line utility has changed)

admin@sonic:~$ show line
  Line    Baud    PID    Start Time    Device
------  ------  -----  ------------  --------
     0       -      -             -
     1    9600      -             -   switch1
     2       -      -             -
     3       -      -             -
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[Blueve]

I will raise another PR to remove this because we need a udev rule update in sonic-buildimage before doing that.