Revert "downgrade server dependency"

This reverts commit 37b4eae.

go.mod

@@ -6,15 +6,14 @@ require (
 	github.com/golang/mock v1.4.4
 	github.com/gorilla/mux v1.8.0
 	github.com/jarcoal/httpmock v1.0.4
-	github.com/mattermost/mattermost-plugin-api v0.0.12
-	github.com/mattermost/mattermost-server/v5 v5.3.2-0.20200731154015-c5c6a5ce5399
+	github.com/mattermost/mattermost-plugin-api v0.0.16
+	github.com/mattermost/mattermost-server/v5 v5.3.2-0.20210621071817-df224571d8a1
 	github.com/mholt/archiver/v3 v3.5.0
 	github.com/niemeyer/pretty v0.0.0-20200227124842-a10e7caefd8e // indirect
 	github.com/pkg/errors v0.9.1
 	github.com/rudderlabs/analytics-go v3.3.1+incompatible
 	github.com/spf13/pflag v1.0.5
 	github.com/stretchr/testify v1.7.0
-	github.com/tidwall/gjson v1.9.4 // indirect
 	github.com/yaegashi/msgraph.go v0.0.0-20191104022859-3f9096c750b2
 	golang.org/x/oauth2 v0.0.0-20200107190931-bf48bf16ab8d
 	gopkg.in/check.v1 v1.0.0-20200227125254-8fa46927fb4f // indirect