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/cache/cache.go

@@ -7,7 +7,7 @@ import (
 	"errors"
 	"time"
 
-	"github.com/mattermost/mattermost-server/v5/model"
+	"github.com/mattermost/mattermost-server/v6/model"
 )
 
 // ErrKeyNotFound is the error when the given key is not found

services/cache/lru.go

@@ -11,7 +11,7 @@ import (
 	"github.com/tinylib/msgp/msgp"
 	"github.com/vmihailenco/msgpack/v5"
 
-	"github.com/mattermost/mattermost-server/v5/model"
+	"github.com/mattermost/mattermost-server/v6/model"
 )
 
 // LRU is a thread-safe fixed size LRU cache.

services/cache/lru_striped.go

@@ -10,7 +10,7 @@ import (
 
 	"github.com/cespare/xxhash/v2"
 
-	"github.com/mattermost/mattermost-server/v5/model"
+	"github.com/mattermost/mattermost-server/v6/model"
 )
 
 // LRUStriped keeps LRU caches in buckets in order to lower mutex contention.

services/cache/lru_striped_bench_test.go

@@ -11,7 +11,7 @@ import (
 
 	"github.com/cespare/xxhash/v2"
 
-	"github.com/mattermost/mattermost-server/v5/services/cache"
+	"github.com/mattermost/mattermost-server/v6/services/cache"
 )
 
 const (

services/cache/lru_striped_test.go

@@ -12,7 +12,7 @@ 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 makeLRUPredictibleTestData(num int) [][2]string {

services/cache/lru_test.go

@@ -12,7 +12,7 @@ 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 TestLRU(t *testing.T) {

services/cache/mocks/Provider.go

@@ -5,7 +5,7 @@ package mocks
 import (
 	mock "github.com/stretchr/testify/mock"
 
-	cache "github.com/mattermost/mattermost-server/v5/services/cache"
+	cache "github.com/mattermost/mattermost-server/v6/services/cache"
 )
 
 // Provider is an autogenerated mock type for the Provider type

services/cache/provider.go

@@ -6,7 +6,7 @@ package cache
 import (
 	"time"
 
-	"github.com/mattermost/mattermost-server/v5/model"
+	"github.com/mattermost/mattermost-server/v6/model"
 )
 
 // CacheOptions contains options for initializaing a cache

services/cache/provider_test.go

@@ -7,7 +7,7 @@ import (
 	"testing"
 	"time"
 
-	"github.com/mattermost/mattermost-server/v5/model"
+	"github.com/mattermost/mattermost-server/v6/model"
 	"github.com/stretchr/testify/require"
 )