gopls: update go.mod for gopls/v0.4.0-pre3

Change-Id: I404653ea908c87c996f54a737ecb9a372022fabe
Reviewed-on: https://go-review.googlesource.com/c/tools/+/227479
Reviewed-by: Peter Weinberger <pjw@google.com>

gopls/go.mod

diff --git a/gopls/go.mod b/gopls/go.mod
index 9868ad5..35523ab 100644
--- a/gopls/go.mod
+++ b/gopls/go.mod
@@ -4,7 +4,7 @@
 
 require (
 	github.com/sergi/go-diff v1.1.0
-	golang.org/x/tools v0.0.0-20200406211959-b2e691980a9d
+	golang.org/x/tools v0.0.0-20200407041343-bf15fae40dea
 	honnef.co/go/tools v0.0.1-2020.1.3
 	mvdan.cc/xurls/v2 v2.1.0
 )