_content/blog/heroku: avoid markdown syntax in summary line

Fixes golang/go#52616

Change-Id: If5326a9098e17d239fe1c6ed340515347dd57ad1
Reviewed-on: https://go-review.googlesource.com/c/website/+/403577
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Benny Siegert <bsiegert@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
diff --git a/_content/blog/heroku.md b/_content/blog/heroku.md
index 9434fb2..8f64636 100644
--- a/_content/blog/heroku.md
+++ b/_content/blog/heroku.md
@@ -6,7 +6,7 @@
 - Blake Mizerany
 tags:
 - guest
-summary: "_This week’s blog post is written by_ [_Keith Rarick_](http://xph.us/) _and_ [_Blake Mizerany_](http://itsbonus.heroku.com/), _systems engineers at_ [Heroku](http://www.heroku.com/). _In their own words, they \"eat, drink, and sleep distributed systems.\" Here they discuss their experiences using Go._"
+summary: Two Heroku system engineers discuss their experiences using Go.
 ---