fix some more style-guide violations in the alert-messages

javascript/ql/src/Expressions/DuplicateProperty.ql

@@ -21,4 +21,4 @@ where
   i < j and
   // only report the next duplicate
   not exists(int mid | mid in [i + 1 .. j - 1] | dpid.same(oe.getProperty(mid).getInit()))
-select p, "This property is duplicated $@.", q, "here"
+select p, "This property is duplicated $@.", q, "in a later property"

javascript/ql/src/Expressions/StringInsteadOfRegex.ql

@@ -56,5 +56,5 @@ where
   s = raw.substring(1, raw.length() - 1) and
   s.regexpMatch(getALikelyRegExpPattern())
 select mce,
-  "String argument '$@' looks like a regular expression, but it will be interpreted as a string.",
+  "String argument $@ looks like a regular expression, but it will be interpreted as a string.",
   arg, s

javascript/ql/src/Expressions/UnboundEventHandlerReceiver.ql

@@ -98,5 +98,5 @@ where
   unbound.getBinder() = callback.getBody() and
   not isBoundInMethod(callback)
 select attribute,
-  "The receiver of this event handler call is unbound, `$@` will be `undefined` in the call to $@",
+  "The receiver of this event handler call is unbound, `$@` will be `undefined` in the call to $@.",
   unbound, "this", callback, callback.getName()