MM-57245: Bump up Go version to 1.21 (#26512)

* MM-57245: Bump up Go version to 1.21

https://mattermost.atlassian.net/browse/MM-57245
```release-note
NONE
```

server/cmd/mmctl/commands/logs_test.go

@@ -32,7 +32,7 @@ func (s *MmctlUnitTestSuite) TestLogsCmd() {
 
 		s.client.
 			EXPECT().
-			GetLogs(context.Background(), 0, 1).
+			GetLogs(context.TODO(), 0, 1).
 			Return(mockSingleLogLine, &model.Response{}, nil).
 			Times(1)
 
@@ -49,7 +49,7 @@ func (s *MmctlUnitTestSuite) TestLogsCmd() {
 
 		s.client.
 			EXPECT().
-			GetLogs(context.Background(), 0, 0).
+			GetLogs(context.TODO(), 0, 0).
 			Return(mockSingleLogLine, &model.Response{}, nil).
 			Times(1)
 
@@ -68,7 +68,7 @@ func (s *MmctlUnitTestSuite) TestLogsCmd() {
 
 		s.client.
 			EXPECT().
-			GetLogs(context.Background(), 0, 1).
+			GetLogs(context.TODO(), 0, 1).
 			Return(mockSingleLogLine, &model.Response{}, nil).
 			Times(1)