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/license_test.go

@@ -25,7 +25,7 @@ func (s *MmctlUnitTestSuite) TestRemoveLicenseCmd() {
 
 		s.client.
 			EXPECT().
-			RemoveLicenseFile(context.Background()).
+			RemoveLicenseFile(context.TODO()).
 			Return(&model.Response{StatusCode: http.StatusBadRequest}, nil).
 			Times(1)
 
@@ -42,7 +42,7 @@ func (s *MmctlUnitTestSuite) TestRemoveLicenseCmd() {
 
 		s.client.
 			EXPECT().
-			RemoveLicenseFile(context.Background()).
+			RemoveLicenseFile(context.TODO()).
 			Return(&model.Response{StatusCode: http.StatusBadRequest}, mockErr).
 			Times(1)
 
@@ -72,7 +72,7 @@ func (s *MmctlUnitTestSuite) TestUploadLicenseCmdF() {
 		printer.Clean()
 		s.client.
 			EXPECT().
-			UploadLicenseFile(context.Background(), mockLicenseFile).
+			UploadLicenseFile(context.TODO(), mockLicenseFile).
 			Return(&model.Response{StatusCode: http.StatusOK}, nil).
 			Times(1)
 
@@ -86,7 +86,7 @@ func (s *MmctlUnitTestSuite) TestUploadLicenseCmdF() {
 		errMsg := "open " + path + ": no such file or directory"
 		s.client.
 			EXPECT().
-			UploadLicenseFile(context.Background(), mockLicenseFile).
+			UploadLicenseFile(context.TODO(), mockLicenseFile).
 			Times(0)
 
 		err := uploadLicenseCmdF(s.client, &cobra.Command{}, []string{path})
@@ -110,7 +110,7 @@ func (s *MmctlUnitTestSuite) TestUploadLicenseStringCmdF() {
 		printer.Clean()
 		s.client.
 			EXPECT().
-			UploadLicenseFile(context.Background(), mockLicenseFile).
+			UploadLicenseFile(context.TODO(), mockLicenseFile).
 			Return(&model.Response{StatusCode: http.StatusOK}, nil).
 			Times(1)