eliminate dmidecode because it requires root privileges (sonic-net#17509)

Why I did it
As described in sonic-net#16878, every show command on the N3248TE-ON results in an error about dmidecode not being found. This is because that command is called in the get_bios_version function of component.py, which is used in a lot of places (many which should not require privileged access).

The error message prior to this change:

jdt@sonic:~$ show system-health
failed to import plugin show.plugins.cisco-8000: [Errno 2] No such file or directory: 'dmidecode'
Usage: show system-health [OPTIONS] COMMAND [ARGS]...

  Show system-health information

How I did it
On this platform, at least, the BIOS version can be obtained from /sys/class/dmi/id/bios_versionwithout requiring root privileges. I adjusted component.py to use that instead of dmidecode.

How to verify it
With that change in place, you can see that commands no longer complain about dmidecode:

Author: justindthomas

platform/broadcom/sonic-platform-modules-dell/n3248te/sonic_platform/component.py

@@ -16,7 +16,7 @@
 except ImportError as e:
     raise ImportError(str(e) + "- required module not found")
 def get_bios_version():
-    return subprocess.check_output(['dmidecode', '-s', 'system-version']).strip().decode()
+    return subprocess.check_output(['cat', '/sys/class/dmi/id/bios_version']).strip().decode()
 
 def get_cpld_version(cpld):
     mjr_ver_path = '/sys/devices/platform/dell-n3248te-cpld.0/' + cpld + '_mjr_ver'