_content/blog: fix a typo in loopvar-preview summary

s/one the most/one of the most/

Change-Id: I196ac2a597713ea71da2d7af5b1e582114a95d71
Reviewed-on: https://go-review.googlesource.com/c/website/+/529096
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
Auto-Submit: Russ Cox <rsc@golang.org>
diff --git a/_content/blog/loopvar-preview.md b/_content/blog/loopvar-preview.md
index ed0d629..f73643c 100644
--- a/_content/blog/loopvar-preview.md
+++ b/_content/blog/loopvar-preview.md
@@ -9,7 +9,7 @@
 
 Go 1.21 includes a preview of a change to `for` loop scoping
 that we plan to ship in Go 1.22,
-removing one the most common Go mistakes.
+removing one of the most common Go mistakes.
 
 ## The Problem