MAINTAINERS: fix style in KEYS-TRUSTED entry

Mimi Zohar used spaces instead of a tab when adding Jarkko Sakkinen as
further maintainer to the KEYS-TRUSTED section entry.

In fact, ./scripts/checkpatch.pl -f MAINTAINERS complains:

  WARNING: MAINTAINERS entries use one tab after TYPE:
  #8581: FILE: MAINTAINERS:8581:
  +M:      Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

The issue was detected when writing a script that parses MAINTAINERS.

Fixes: 34bccd61 ("MAINTAINERS: add Jarkko as maintainer for trusted keys")
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Acked-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>