lscpu: remove extra space from field key name

lscpu: remove extra space from field key name

The extra space was more obvious in json output.  But as the expected test
output displays also the standard output can be effected by this change.

    $ lscpu --json | jq '.lscpu | .[].field' | grep ': '
    "L1d cache: "
    "L1i cache: "
    "L2 cache: "
    "L3 cache: "
    "Vulnerability L1tf: "
    "Vulnerability Mds: "
    "Vulnerability Meltdown: "
    "Vulnerability Spec store bypass: "
    "Vulnerability Spectre v1: "
    "Vulnerability Spectre v2: "

Signed-off-by: Sami Kerola <kerolasa@iki.fi>