doc: make symbol links simpler for relnotes

This is a follow-up to CL 578195.

Change-Id: I6466ff8753f05a9424a8098cd88490aab6b236c9
Reviewed-on: https://go-review.googlesource.com/c/go/+/580277
Reviewed-by: Dmitri Shuralyov <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Auto-Submit: Dmitri Shuralyov <[email protected]>
Reviewed-by: Jonathan Amsterdam <[email protected]>

Author: callthingsoff

doc/next/6-stdlib/99-minor/go/types/65772.md

@@ -1,4 +1,3 @@
-The [`Func`](/go/types#Func) type, which represents a function or
-method symbol, now has a [`Signature`](/go/types#Func.Signature)
-method that returns the function's type, which is always a
-`Signature`.
+The [Func] type, which represents a function or method symbol, now
+has a [Func.Signature] method that returns the function's type, which
+is always a `Signature`.

doc/next/6-stdlib/99-minor/net/http/46443.md

@@ -1,3 +1,3 @@
-[`Cookie`](/pkg/net/http#Cookie) now preserves double quotes surrounding
-a cookie value. The new `Cookie.Quoted` field indicates whether the
-`Cookie.Value` was originally quoted.
+[Cookie] now preserves double quotes surrounding a cookie value.
+The new [Cookie.Quoted] field indicates whether the [Cookie.Value]
+was originally quoted.