Simplified comments for NewImplicitDirInode.
Simplified comments for NewImplicitDirInode.

BanzaiMan/gcsfuse,GoogleCloudPlatform/gcsfuse,kahing/gcsfuse,GoogleCloudPlatform/gcsfuse,jacobsa/timeutil,mbrukman/gcsfuse,jacobsa/ratelimit,BanzaiMan/gcsfuse,GoogleCloudPlatform/gcsfuse