doc/go1.7.html: add missing <code> and </a>

Change-Id: I5f4bf89345dc139063dcf34da653e914386bcde6
Reviewed-on: https://go-review.googlesource.com/23735Reviewed-by: Ian Lance Taylor <iant@golang.org>

doc/go1.7.html

@@ -401,7 +401,8 @@ See the <a href="/pkg/testing/#hdr-Subtests_and_Sub_benchmarks">package document
 
 <p>
 All panics started by the runtime now use panic values
-that implement both the builtin <a href="/ref/spec#Errors">error</code>,
+that implement both the
+builtin <a href="/ref/spec#Errors"><code>error</code></a>,
 and
 <a href="/pkg/runtime/#Error"><code>runtime.Error</code></a>,
 as