Update configure-a-hidden-replica-set-member.txt

The use of letter 'a' is not grammatically correct here.

Author: askmrsinh

source/tutorial/configure-a-hidden-replica-set-member.txt

@@ -12,7 +12,7 @@ Configure a Hidden Replica Set Member
 
 Hidden members are part of a :term:`replica set` but cannot become
 :term:`primary` and are invisible to client applications. Hidden members
-may vote in :ref:`elections <replica-set-elections>`. For a
+may vote in :ref:`elections <replica-set-elections>`. For
 more information on hidden members and their uses, see
 :doc:`/core/replica-set-hidden-member`.