MM-36271: Bump major version to 6.0 (#17973)

https://mattermost.atlassian.net/browse/MM-36271

```release-note
We bump the major version to 6.0
```

migrations/advanced_permissions_phase_2.go

@@ -9,7 +9,7 @@ import (
 	"net/http"
 	"strings"
 
-	"github.com/mattermost/mattermost-server/v5/model"
+	"github.com/mattermost/mattermost-server/v6/model"
 )
 
 type AdvancedPermissionsPhase2Progress struct {

migrations/helper_test.go

@@ -6,12 +6,12 @@ package migrations
 import (
 	"os"
 
-	"github.com/mattermost/mattermost-server/v5/app"
-	"github.com/mattermost/mattermost-server/v5/app/request"
-	"github.com/mattermost/mattermost-server/v5/config"
-	"github.com/mattermost/mattermost-server/v5/model"
-	"github.com/mattermost/mattermost-server/v5/store/localcachelayer"
-	"github.com/mattermost/mattermost-server/v5/utils"
+	"github.com/mattermost/mattermost-server/v6/app"
+	"github.com/mattermost/mattermost-server/v6/app/request"
+	"github.com/mattermost/mattermost-server/v6/config"
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/store/localcachelayer"
+	"github.com/mattermost/mattermost-server/v6/utils"
 )
 
 type TestHelper struct {

migrations/main_test.go

@@ -6,8 +6,8 @@ package migrations
 import (
 	"testing"
 
-	"github.com/mattermost/mattermost-server/v5/shared/mlog"
-	"github.com/mattermost/mattermost-server/v5/testlib"
+	"github.com/mattermost/mattermost-server/v6/shared/mlog"
+	"github.com/mattermost/mattermost-server/v6/testlib"
 )
 
 var mainHelper *testlib.MainHelper

migrations/migrations.go

@@ -6,10 +6,10 @@ package migrations
 import (
 	"net/http"
 
-	"github.com/mattermost/mattermost-server/v5/app"
-	tjobs "github.com/mattermost/mattermost-server/v5/jobs/interfaces"
-	"github.com/mattermost/mattermost-server/v5/model"
-	"github.com/mattermost/mattermost-server/v5/store"
+	"github.com/mattermost/mattermost-server/v6/app"
+	tjobs "github.com/mattermost/mattermost-server/v6/jobs/interfaces"
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/store"
 )
 
 const (

migrations/migrations_test.go

@@ -9,7 +9,7 @@ import (
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
-	"github.com/mattermost/mattermost-server/v5/model"
+	"github.com/mattermost/mattermost-server/v6/model"
 )
 
 func TestGetMigrationState(t *testing.T) {

migrations/scheduler.go

@@ -6,9 +6,9 @@ package migrations
 import (
 	"time"
 
-	"github.com/mattermost/mattermost-server/v5/app"
-	"github.com/mattermost/mattermost-server/v5/model"
-	"github.com/mattermost/mattermost-server/v5/shared/mlog"
+	"github.com/mattermost/mattermost-server/v6/app"
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/shared/mlog"
 )
 
 const (

migrations/worker.go

@@ -8,10 +8,10 @@ import (
 	"net/http"
 	"time"
 
-	"github.com/mattermost/mattermost-server/v5/app"
-	"github.com/mattermost/mattermost-server/v5/jobs"
-	"github.com/mattermost/mattermost-server/v5/model"
-	"github.com/mattermost/mattermost-server/v5/shared/mlog"
+	"github.com/mattermost/mattermost-server/v6/app"
+	"github.com/mattermost/mattermost-server/v6/jobs"
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/shared/mlog"
 )
 
 const (