doc/go1.18: drop TODO for "Changes to the language"

For #47694

Change-Id: I142776001eecb451e8722163cfd3f2ecb0ecf35c
Reviewed-on: https://go-review.googlesource.com/c/go/+/369980
Trust: Austin Clements <[email protected]>
Reviewed-by: Jeremy Faller <[email protected]>

Author: aclements

doc/go1.18.html

@@ -25,10 +25,6 @@ <h2 id="introduction">DRAFT RELEASE NOTES — Introduction to Go 1.18</h2>
 
 <h2 id="language">Changes to the language</h2>
 
-<p>
-  TODO: complete this section
-</p>
-
 <h3 id="generics">Generics</h3>
 
 <p><!-- https://golang.org/issue/43651, https://golang.org/issue/45346 -->