doc/go1.13: close <em> and <code> tags

Fixup for two typos from CL 183630.

Change-Id: I7968a736680e8a6bbd1f4691d443b217702bc190
Reviewed-on: https://go-review.googlesource.com/c/go/+/183843Reviewed-by: Bryan C. Mills <bcmills@google.com>

doc/go1.13.html

@@ -270,7 +270,7 @@ go env -w GOSUMDB=off
   Additionally, the <code>go</code> <code>get</code> subcommand now supports
   the <code>-t</code> flag in module-aware mode. As in GOPATH mode,
   the <code>-t</code> flag instructs <code>go</code> <code>get</code> to include
-  the packages imported by <em>tests of<em> the packages named on the command
+  the packages imported by <em>tests of</em> the packages named on the command
   line. If the <code>-t</code> flag is set, the packages imported by tests will
   be updated (if the <code>-u</code> flag is set), downloaded, and built (unless
   the <code>-d</code> flag is set) along with the usual non-test packages.
@@ -312,7 +312,7 @@ go env -w GOSUMDB=off
   <a href="/cmd/go/#hdr-The_main_module_and_the_build_list">main module</a> uses
   an invalid pseudo-version, it can usually be corrected by redacting the
   version to just the commit hash and re-running a <code>go</code> command, such
-  as <code>go</coqde> <code>list</code> <code>-m</code> <code>all</code>
+  as <code>go</code> <code>list</code> <code>-m</code> <code>all</code>
   or <code>go</code> <code>mod</code> <code>tidy</code>. For example,
 </p>
 <pre>require github.com/docker/docker v1.14.0-0.20190319215453-e7b5f7dbe98c</pre>