boards: scobc_a1: Fix YAMLLint error

Fixes the YAMLLint error as below:

   YAMLLint (indentation):wrong indentation: expected 4 but found 2
   File:boards/sc/scobc_a1/board.yml
   Line:12
   Column:3

Signed-off-by: Takuya Sasaki <takuya.sasaki@spacecubics.com>