_content/blog: fix typo

Change-Id: Id5d5b34dbad33ee3c669b0aef9dad738ae9dc99e
Reviewed-on: https://go-review.googlesource.com/c/website/+/474076
Run-TryBot: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Carlos Amedee <carlos@golang.org>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>

_content/blog/first-go-program.md

@@ -23,7 +23,7 @@ in an old message to Robert and Ken Thompson.
 What follows is the first Go program. It was written by Rob in February 2008,
 when the team was just Rob, Robert, and Ken. They had a solid feature list
 (mentioned in [this blog post](https://commandcenter.blogspot.com.au/2012/06/less-is-exponentially-more.html))
-and a rough language specfication. Ken had just finished the first working version of
+and a rough language specification. Ken had just finished the first working version of
 a Go compiler (it didn't produce native code, but rather transliterated Go code
 to C for fast prototyping) and it was time to try writing a program with it.