MM-53032: Fix module path after repo rename (#23689)

It was a good decision in hindsight to keep the public module as 0.x
because this would have been a breaking change again.

https://mattermost.atlassian.net/browse/MM-53032
```release-note
Changed the Go module path from github.com/mattermost/mattermost-server/server/v8 to github.com/mattermost/mattermost/server/v8.

For the public facing module, it's path is also changed from github.com/mattermost/mattermost-server/server/public to github.com/mattermost/mattermost/server/public
```

server/platform/services/slackimport/converters.go

@@ -8,7 +8,7 @@ import (
 	"strconv"
 	"strings"
 
-	"github.com/mattermost/mattermost-server/server/public/shared/mlog"
+	"github.com/mattermost/mattermost/server/public/shared/mlog"
 )
 
 func slackConvertTimeStamp(ts string) int64 {

server/platform/services/slackimport/parsers.go

@@ -7,8 +7,8 @@ import (
 	"encoding/json"
 	"io"
 
-	"github.com/mattermost/mattermost-server/server/public/model"
-	"github.com/mattermost/mattermost-server/server/public/shared/mlog"
+	"github.com/mattermost/mattermost/server/public/model"
+	"github.com/mattermost/mattermost/server/public/shared/mlog"
 )
 
 func slackParseChannels(data io.Reader, channelType model.ChannelType) ([]slackChannel, error) {

server/platform/services/slackimport/slackimport.go

@@ -18,12 +18,12 @@ import (
 	"time"
 	"unicode/utf8"
 
-	"github.com/mattermost/mattermost-server/server/public/model"
-	"github.com/mattermost/mattermost-server/server/public/shared/i18n"
-	"github.com/mattermost/mattermost-server/server/public/shared/mlog"
-	"github.com/mattermost/mattermost-server/server/v8/channels/app/request"
-	"github.com/mattermost/mattermost-server/server/v8/channels/store"
-	"github.com/mattermost/mattermost-server/server/v8/channels/utils"
+	"github.com/mattermost/mattermost/server/public/model"
+	"github.com/mattermost/mattermost/server/public/shared/i18n"
+	"github.com/mattermost/mattermost/server/public/shared/mlog"
+	"github.com/mattermost/mattermost/server/v8/channels/app/request"
+	"github.com/mattermost/mattermost/server/v8/channels/store"
+	"github.com/mattermost/mattermost/server/v8/channels/utils"
 )
 
 type slackChannel struct {

server/platform/services/slackimport/slackimport_test.go

@@ -12,10 +12,10 @@ import (
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
-	"github.com/mattermost/mattermost-server/server/public/model"
-	"github.com/mattermost/mattermost-server/server/public/shared/mlog"
-	"github.com/mattermost/mattermost-server/server/v8/channels/app/request"
-	"github.com/mattermost/mattermost-server/server/v8/channels/store/storetest/mocks"
+	"github.com/mattermost/mattermost/server/public/model"
+	"github.com/mattermost/mattermost/server/public/shared/mlog"
+	"github.com/mattermost/mattermost/server/v8/channels/app/request"
+	"github.com/mattermost/mattermost/server/v8/channels/store/storetest/mocks"
 )
 
 func TestSlackConvertTimeStamp(t *testing.T) {