doc/contribute.html: add whitespace after <code> blocks, where missing

Change-Id: Iea5c705dd58f9b83fbeb0500defcc08c34716169
GitHub-Last-Rev: 35702c784e2329fe3e44947430d246f8cdb04645
GitHub-Pull-Request: golang/go#25858
Reviewed-on: https://go-review.googlesource.com/118536Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

doc/contribute.html

@@ -418,7 +418,7 @@ $ ./all.bash    # recompile and test
 
 <li>
 <b>Step 4:</b> Send the changes for review to Gerrit using <code>git</code>
-<code>codereview</code> <code>mail</code>(which doesn't use e-mail, despite the name).
+<code>codereview</code> <code>mail</code> (which doesn't use e-mail, despite the name).
 <pre>
 $ git codereview mail     # send changes to Gerrit
 </pre>
@@ -984,8 +984,8 @@ followed by <code>run.bash</code>.
 
 <li>
 In this section, we'll call the directory into which you cloned the Go repository <code>$GODIR</code>.
-The <code>go</code> tool built by <code>$GODIR/make.bash</code>will be installed
-in <code>$GODIR/bin/go</code>and you
+The <code>go</code> tool built by <code>$GODIR/make.bash</code> will be installed
+in <code>$GODIR/bin/go</code> and you
 can invoke it to test your code.
 For instance, if you
 have modified the compiler and you want to test how it affects the