present: reformat doc comment for lack of inline code

Fixes golang/go#58999

Change-Id: I65886cd5b80b022b038462b8040453feafaaf7b2
Reviewed-on: https://go-review.googlesource.com/c/tools/+/475975
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
gopls-CI: kokoro <noreply+kokoro@google.com>
Reviewed-by: Russ Cox <rsc@golang.org>

present/doc.go

@@ -200,8 +200,11 @@ There must be no spaces between markers. Within marked text,
 a single marker character becomes a space and a doubled single
 marker quotes the marker character.
 
-Links can be included in any text with the form [[url][label]], or
-[[url]] to use the URL itself as the label.
+Links can be included in any text with either explicit labels
+or the URL itself as the label. For example:
+
+	[[url][label]]
+	[[url]]
 
 # Command Invocations