Maintainers.txt: Remove Orphan status option

We would like any proposed change in the edk2 codebase to be
assignable to a human maintainer/reviewer. If there is a feature
for which there is no longer any support, we should find a way
to remove it from the head of the repository. For critical
features, we must find community members that are willing to
own it.

Cc: Andrew Fish <afish@apple.com>
Cc: Leif Lindholm <quic_llindhol@quicinc.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Leif Lindholm <quic_llindhol@quicinc.com>

Maintainers.txt

@@ -31,8 +31,6 @@ Descriptions of section entries:
      Maintained: Someone actually looks after it.
      Odd Fixes:  It has a maintainer but they don't have time to do
                  much other than throw the odd patch in. See below.
-     Orphan:     No current maintainer [but maybe you could take the
-                 role as you write your new code].
      Obsolete:   Old code. Something tagged obsolete generally means
                  it has been replaced by a better system and you
                  should be using that.