gopls/doc: fix broken url

Change-Id: Ieba27ec81f641928bb12467e8cc08bc63ffaa34a
Reviewed-on: https://go-review.googlesource.com/c/tools/+/695575
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: David Chase <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>
Reviewed-by: Alberto Donizetti <[email protected]>
Auto-Submit: Dmitri Shuralyov <[email protected]>

Author: cuishuang

gopls/doc/index.md

@@ -130,7 +130,7 @@ and
 ### Supported Go versions
 
 `gopls` follows the
-[Go Release Policy](https://golang.org/devel/release.html#policy), meaning
+[Go Release Policy](https://go.dev/doc/devel/release#policy), meaning
 that it officially supports only the two most recent major Go releases.
 
 When using gopls, there are three versions to be aware of: