Update vendor directory

vendor/golang.org/x/net/http2/not_go18.go

@@ -6,7 +6,10 @@
 
 package http2
 
-import "net/http"
+import (
+	"io"
+	"net/http"
+)
 
 func configureServer18(h1 *http.Server, h2 *Server) error {
 	// No IdleTimeout to sync prior to Go 1.8.
@@ -16,3 +19,9 @@ func configureServer18(h1 *http.Server, h2 *Server) error {
 func shouldLogPanic(panicValue interface{}) bool {
 	return panicValue != nil
 }
+
+func reqGetBody(req *http.Request) func() (io.ReadCloser, error) {
+	return nil
+}
+
+func reqBodyIsNoBody(io.ReadCloser) bool { return false }