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
```

services/telemetry/mocks/ServerIface.go

@@ -7,12 +7,12 @@ package mocks
 import (
 	context "context"
 
-	httpservice "github.com/mattermost/mattermost-server/v5/services/httpservice"
+	httpservice "github.com/mattermost/mattermost-server/v6/services/httpservice"
 	mock "github.com/stretchr/testify/mock"
 
-	model "github.com/mattermost/mattermost-server/v5/model"
+	model "github.com/mattermost/mattermost-server/v6/model"
 
-	plugin "github.com/mattermost/mattermost-server/v5/plugin"
+	plugin "github.com/mattermost/mattermost-server/v6/plugin"
 )
 
 // ServerIface is an autogenerated mock type for the ServerIface type

services/telemetry/telemetry.go

@@ -13,14 +13,14 @@ import (
 
 	rudder "github.com/rudderlabs/analytics-go"
 
-	"github.com/mattermost/mattermost-server/v5/model"
-	"github.com/mattermost/mattermost-server/v5/plugin"
-	"github.com/mattermost/mattermost-server/v5/services/httpservice"
-	"github.com/mattermost/mattermost-server/v5/services/marketplace"
-	"github.com/mattermost/mattermost-server/v5/services/searchengine"
-	"github.com/mattermost/mattermost-server/v5/shared/mlog"
-	"github.com/mattermost/mattermost-server/v5/store"
-	"github.com/mattermost/mattermost-server/v5/utils"
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/plugin"
+	"github.com/mattermost/mattermost-server/v6/services/httpservice"
+	"github.com/mattermost/mattermost-server/v6/services/marketplace"
+	"github.com/mattermost/mattermost-server/v6/services/searchengine"
+	"github.com/mattermost/mattermost-server/v6/shared/mlog"
+	"github.com/mattermost/mattermost-server/v6/store"
+	"github.com/mattermost/mattermost-server/v6/utils"
 )
 
 const (

services/telemetry/telemetry_test.go

@@ -19,14 +19,14 @@ import (
 	"github.com/stretchr/testify/mock"
 	"github.com/stretchr/testify/require"
 
-	"github.com/mattermost/mattermost-server/v5/model"
-	"github.com/mattermost/mattermost-server/v5/plugin"
-	"github.com/mattermost/mattermost-server/v5/plugin/plugintest"
-	"github.com/mattermost/mattermost-server/v5/services/httpservice"
-	"github.com/mattermost/mattermost-server/v5/services/searchengine"
-	"github.com/mattermost/mattermost-server/v5/services/telemetry/mocks"
-	"github.com/mattermost/mattermost-server/v5/shared/mlog"
-	storeMocks "github.com/mattermost/mattermost-server/v5/store/storetest/mocks"
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/plugin"
+	"github.com/mattermost/mattermost-server/v6/plugin/plugintest"
+	"github.com/mattermost/mattermost-server/v6/services/httpservice"
+	"github.com/mattermost/mattermost-server/v6/services/searchengine"
+	"github.com/mattermost/mattermost-server/v6/services/telemetry/mocks"
+	"github.com/mattermost/mattermost-server/v6/shared/mlog"
+	storeMocks "github.com/mattermost/mattermost-server/v6/store/storetest/mocks"
 )
 
 type FakeConfigService struct {