rm memcg type from ignore list.

This type was removed in commit: 93166cef
and no longer needs to be included in compatibility infrastructure.

Bug: 62573845
Test: None, prebuilt change.
Change-Id: I9dc05512c7fcb3ef4445c4c6b040809a1d595282

prebuilts/api/26.0/26.0.ignore.cil

@@ -9,7 +9,6 @@
     hal_cas_hwservice
     hal_tetheroffload_hwservice
     kmsg_debug_device
-    memcg_device
     netd_stable_secret_prop
     sysfs_fs_ext4_features
     timezone_service