samples: sensor: Update sensor shell documentation
samples: sensor: Update sensor shell documentation

Updates the sensor shell sample documentation to reflect the currently
supported sensor shell commands. The list and list_channels commands
were removed in commit 95b4d37230b3942460eeb18f608a40f95e0c2b90 but the
documentation wasn't updated at the time.

Signed-off-by: Maureen Helm <87a696db5547fa477bda9f9e0f00013c839c14d3@intel.com>

galak/zephyr,finikorg/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr,finikorg/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr