gopls: update go.mod for v0.4.3-pre2

Change-Id: I4ae900a1e3a4fbaad9ff8304a67c2dd514a505ae
Reviewed-on: https://go-review.googlesource.com/c/tools/+/241523
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
Reviewed-by: Heschi Kreinick <heschi@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

gopls/go.mod

@@ -4,7 +4,7 @@ go 1.13
 
 require (
 	github.com/sergi/go-diff v1.1.0
-	golang.org/x/tools v0.0.0-20200708171055-22d49bd2bae0
+	golang.org/x/tools v0.0.0-20200708181441-6004c8539734
 	honnef.co/go/tools v0.0.1-2020.1.4
 	mvdan.cc/xurls/v2 v2.2.0
 )