go.sum: add golang.org/x/tools sum

The go.mod sum was present, but not the module sum.

Change-Id: I7def303bf4507a88dfa1bb0502116efde4d64b01
Reviewed-on: https://go-review.googlesource.com/c/go/+/203882
Run-TryBot: Josh Bleecher Snyder <[email protected]>
Reviewed-by: Brad Fitzpatrick <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>

Author: josharian

src/go.sum

@@ -11,4 +11,5 @@ golang.org/x/sys v0.0.0-20190529130038-5219a1e1c5f8/go.mod h1:h1NjWce9XRLGQEsW7w
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.2 h1:tW2bmiBqwgJj/UpqtC8EpXEZVYOwU0yG4iWbprSVAcs=
 golang.org/x/text v0.3.2/go.mod h1:bEr9sfX3Q8Zfm5fL9x+3itogRgK3+ptLWKqgva+5dAk=
+golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e h1:FDhOuMEY4JVRztM/gsbk+IKUQ8kj74bxZrgw87eMMVc=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=