update github.com/pelletier/go-toml to 1.2.0

Rationale: github.com/pelletier/go-toml is the only package that currently
prevents the future vendoring of github.com/golang/dep as it depends on
functions introduced in 1.1.0.

The only consumers of this package are github.com/spf13/viper (used to run e2e
tests) and github.com/bazelbuild/bazel-gazelle (bazel helper), so that's a
pretty low-risk change.

vendor/github.com/pelletier/go-toml/token.go

@@ -23,6 +23,8 @@ const (
 	tokenTrue
 	tokenFalse
 	tokenFloat
+	tokenInf
+	tokenNan
 	tokenEqual
 	tokenLeftBracket
 	tokenRightBracket
@@ -55,6 +57,8 @@ var tokenTypeNames = []string{
 	"True",
 	"False",
 	"Float",
+	"Inf",
+	"NaN",
 	"=",
 	"[",
 	"]",