gopls: update go.mod file for v0.5.0-pre1

Change-Id: I50fea8e6d2185bebd811a37ba0ca80a435d01791
Reviewed-on: https://go-review.googlesource.com/c/tools/+/253802
Run-TryBot: Rebecca Stambler <[email protected]>
Reviewed-by: Heschi Kreinick <[email protected]>
TryBot-Result: Gobot Gobot <[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 v0.0.0-20200828161849-5deb26317202
+	golang.org/x/tools v0.0.0-20200909210919-475d9e863437
 	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