Bug#653750: -Tqt: "This an option" -> "This is an option"

[Regid Ichira]

--- /usr/share/doc/exim-base/spec.txt   2012-02-06 16:26:00.505182473 +0200
+++ /usr/share/doc/exim-base/spec.txt.mod       2012-02-06 16:25:14.000000000 +0200
@@ -4151,10 +4151,10 @@ brief message about itself and exits.

 -Tqt <times>

-    This an option that is exclusively for use by the Exim testing suite. It is
-    not recognized when Exim is run normally. It allows for the setting up of
-    explicit "queue times" so that various warning/retry features can be
-    tested.
+    This is an option that is exclusively for use by the Exim testing suite.
+    It is not recognized when Exim is run normally. It allows for the setting
+    up of explicit "queue times" so that various warning/retry features can
+    be tested.

 -t