editorial: fix grammatical error in setGeolocationOverride steps (#893)

Remove the extra "a" in "Set geolocation overrides map[user context] to a command parameters[coordinates]."

Author: reillyeon

index.bs

@@ -5676,7 +5676,7 @@ The [=remote end steps=] with |command parameters| are:
 
    1. For each |user context| of |user contexts|:
 
-      1. [=map/Set=] [=geolocation overrides map=][|user context|] to a |command parameters|["<code>coordinates</code>"].
+      1. [=map/Set=] [=geolocation overrides map=][|user context|] to |command parameters|["<code>coordinates</code>"].
 
       1. [=list/For each=] |top-level traversable| of the list of all [=/top-level traversables=]
          whose [=associated user context=] is |user context|: