Update arbiter-volumes-and-quorum.md (#784)

Fixed typo

docs/Administrator-Guide/arbiter-volumes-and-quorum.md

@@ -182,7 +182,7 @@ The following volume set options are used to configure it:
 > to specify the number of bricks to be active to participate in quorum.
 > If the quorum-type is auto then this option has no significance.
 
-Earlier, when quorm was not met, the replica subvolume turned read-only. But
+Earlier, when quorum was not met, the replica subvolume turned read-only. But
 since [glusterfs-3.13](https://docs.gluster.org/en/latest/release-notes/3.13.0/#addition-of-checks-for-allowing-lookups-in-afr-and-removal-of-clusterquorum-reads-volume-option) and upwards, the subvolume becomes unavailable, i.e. all
 the file operations fail with ENOTCONN error instead of becoming EROFS.
 This means the `cluster.quorum-reads` volume option is also not supported.