gopls: update go.mod for gopls/v0.5.0-pre2

Change-Id: I65b1652b4b6719b6106371698837572362a4ab99
Reviewed-on: https://go-review.googlesource.com/c/tools/+/254557
Run-TryBot: Rebecca Stambler <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>
Reviewed-by: Robert Findley <[email protected]>

Author: stamblerre

gopls/go.mod

@@ -4,7 +4,7 @@ go 1.13
 
 require (
 	github.com/sergi/go-diff v1.1.0
-	golang.org/x/tools v0.0.0-20200909210919-475d9e863437
+	golang.org/x/tools v0.0.0-20200913034212-796b347e00a4
 	golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1
 	honnef.co/go/tools v0.0.1-2020.1.5
 	mvdan.cc/gofumpt v0.0.0-20200802201014-ab5a8192947d