Update module cenkalti/backoff to v2.2.0

Author: renovate-bot

go.mod

@@ -8,7 +8,7 @@ require (
 	github.com/ajg/form v1.5.1 // indirect
 	github.com/aws/aws-lambda-go v1.11.1
 	github.com/aws/aws-sdk-go v1.20.13
-	github.com/cenkalti/backoff v2.0.0+incompatible
+	github.com/cenkalti/backoff v2.2.0+incompatible
 	github.com/certifi/gocertifi v0.0.0-20190629135335-d2eda7129713 // indirect
 	github.com/denisenkom/go-mssqldb v0.0.0-20190629141010-eb9f6a1743f3 // indirect
 	github.com/docker/distribution v2.7.1+incompatible // indirect

go.sum

@@ -27,6 +27,7 @@ github.com/beorn7/perks v0.0.0-20180321164747-3a771d992973/go.mod h1:Dwedo/Wpr24
 github.com/beorn7/perks v1.0.0/go.mod h1:KWe93zE9D1o94FZ5RNwFwVgaQK1VOXiVxmqh+CedLV8=
 github.com/cenkalti/backoff v2.0.0+incompatible h1:5IIPUHhlnUZbcHQsQou5k1Tn58nJkeJL9U+ig5CHJbY=
 github.com/cenkalti/backoff v2.0.0+incompatible/go.mod h1:90ReRw6GdpyfrHakVjL/QHaoyV4aDUVVkXQJJJ3NXXM=
+github.com/cenkalti/backoff v2.2.0+incompatible/go.mod h1:b6Nc7NRH5C4aCISLry0tLnTjcuTEvoiqcWDdsU0sOGM=
 github.com/certifi/gocertifi v0.0.0-20190629135335-d2eda7129713 h1:U2wuyAlXrWQ+MrJdR5vyio9NUNqgnORR94Gq20hIJ6Y=
 github.com/certifi/gocertifi v0.0.0-20190629135335-d2eda7129713/go.mod h1:GJKEexRPVJrBSOjoqN5VNOIKJ5Q3RViH6eu3puDRwx4=
 github.com/cespare/xxhash v1.1.0/go.mod h1:XrSqR1VqqWfGrhpAt58auRo0WTKS1nRRg3ghfAqPWnc=