deb-src-control(5): Fix typo

man/deb-src-control.5

@@ -193,7 +193,7 @@ by a hyphen). Accepted version relationships are ">>" for greater than,
 "<<" for less than, ">=" for greater than or equal to, "<=" for less than
 or equal to, and "=" for equal to.
 
-A architecture specification consists of one or more architecture names,
+An architecture specification consists of one or more architecture names,
 separated by whitespace. Exclamation marks may be prepended to each of the
 names, meaning "NOT".