internal/lsp: update go.mod for next version

Change-Id: Ic2e437f7daec94f648ba1a13e99a9ada462cdf49
Reviewed-on: https://go-review.googlesource.com/c/tools/+/194897
Run-TryBot: Rebecca Stambler <[email protected]>
Reviewed-by: Heschi Kreinick <[email protected]>

Author: stamblerre

gopls/go.mod

@@ -2,6 +2,6 @@ module golang.org/x/tools/gopls
 
 go 1.11
 
-require golang.org/x/tools v0.0.0-20190911193649-b13fa046aa37
+require golang.org/x/tools v0.0.0-20190911225940-c7d52e45e2f2
 
 replace golang.org/x/tools => ../