doc: update tzdata version in 1.12 release notes

It was recently updated (again) to version 2018i. Since we're here,
wrap the paragraph at ~70 columns, like all the others.

Change-Id: I0a380385f34f1df1258a9f2af447234967422f37
Reviewed-on: https://go-review.googlesource.com/c/156857Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

doc/go1.12.html

@@ -545,7 +545,10 @@ for {
 <dl id="lib/time"><dt><a href="/pkg/lib/time/">lib/time</a></dt>
   <dd>
     <p><!-- CL 151299 -->
-    The time zone database in <code>$GOROOT/lib/time/zoneinfo.zip</code> has been updated to version 2018g. Note that this ZIP file is only used if a time zone database is not provided by the operating system.
+      The time zone database in <code>$GOROOT/lib/time/zoneinfo.zip</code>
+      has been updated to version 2018i. Note that this ZIP file is
+      only used if a time zone database is not provided by the operating
+      system.
     </p>
 
 </dl><!-- lib/time -->