spec: typographical adjustment for ellipsis

The paragraph describing the ellipses presents the horizontal ellipsis
in two different fonts and at least on my screen they look too different.
Switch to a consistent rendering.

Of small steps are great journeys undertaken.

R=golang-dev, rsc, dsymonds, gri
CC=golang-dev
https://golang.org/cl/5650055

doc/go_spec.html

 <!--{
 	"Title": "The Go Programming Language Specification",
-	"Subtitle": "Version of February 8, 2012"
+	"Subtitle": "Version of February 13, 2012"
 }-->
 
 <!--
@@ -74,8 +74,8 @@ double quotes <code>""</code> or back quotes <code>``</code>.
 <p>
 The form <code>a … b</code> represents the set of characters from
 <code>a</code> through <code>b</code> as alternatives. The horizontal
-ellipis … is also used elsewhere in the spec to informally denote various
-enumerations or code snippets that are not further specified. The character …
+ellipis <code>…</code> is also used elsewhere in the spec to informally denote various
+enumerations or code snippets that are not further specified. The character <code>…</code>
 (as opposed to the three characters <code>...</code>) is not a token of the Go
 language.
 </p>