completions: Use only spaces in indent
completions: Use only spaces in indent

Since both of tabs and spaces in indentation were used and
there were tabs expected 4 spaces width and 8 spaces width,
only spaces use in indentation.

Signed-off-by: ERAMOTO Masaya <495370e91cae577581028a5efee5824f74357ca0@jp.fujitsu.com>

mtrmac/skopeo,mtrmac/skopeo,mtrmac/skopeo