design/51082-godocfmt: fix typo

Change-Id: I6d56cf8ac019ce383b856be5e7cfec8b532173ad
GitHub-Last-Rev: 7349441d7f457f83c00b3820441c010719c99c68
GitHub-Pull-Request: golang/proposal#40
Reviewed-on: https://go-review.googlesource.com/c/proposal/+/386318
Reviewed-by: Ian Lance Taylor <iant@golang.org>
diff --git a/design/51082-godocfmt.md b/design/51082-godocfmt.md
index 8a9c586..d2509df 100644
--- a/design/51082-godocfmt.md
+++ b/design/51082-godocfmt.md
@@ -388,7 +388,7 @@
  - All numbered list items use the “N.” form (“N)” is converted).
  - The ASCII double-single-quote forms that have always been
    defined to render as “ and ” are replaced with those.
- - Link URL definitionss are moved to the bottom of the doc comment,
+ - Link URL definitions are moved to the bottom of the doc comment,
    in two different blank-line-separated groups:
    definitions used by the doc comment
    and definitions not used.