Fix DBConsistency checks on MSSQL (go-gitea#23132)

Unfortunately xorm's `builder.Select(...).From(...)` does not escape the
table names. This is mostly not a problem but is a problem with the
`user` table.

This PR simply escapes the user table. No other uses of `From("user")`
where found in the codebase so I think this should be all that is
needed.

Fix go-gitea#23064

Signed-off-by: Andrew Thornton <art27@cantab.net>

models/issues/label.go

@@ -755,7 +755,7 @@ func CountOrphanedLabels() (int64, error) {
 	norepo, err := db.GetEngine(db.DefaultContext).Table("label").
 		Where(builder.And(
 			builder.Gt{"repo_id": 0},
-			builder.NotIn("repo_id", builder.Select("id").From("repository")),
+			builder.NotIn("repo_id", builder.Select("id").From("`repository`")),
 		)).
 		Count()
 	if err != nil {
@@ -765,7 +765,7 @@ func CountOrphanedLabels() (int64, error) {
 	noorg, err := db.GetEngine(db.DefaultContext).Table("label").
 		Where(builder.And(
 			builder.Gt{"org_id": 0},
-			builder.NotIn("org_id", builder.Select("id").From("user")),
+			builder.NotIn("org_id", builder.Select("id").From("`user`")),
 		)).
 		Count()
 	if err != nil {
@@ -786,7 +786,7 @@ func DeleteOrphanedLabels() error {
 	if _, err := db.GetEngine(db.DefaultContext).
 		Where(builder.And(
 			builder.Gt{"repo_id": 0},
-			builder.NotIn("repo_id", builder.Select("id").From("repository")),
+			builder.NotIn("repo_id", builder.Select("id").From("`repository`")),
 		)).
 		Delete(Label{}); err != nil {
 		return err
@@ -796,7 +796,7 @@ func DeleteOrphanedLabels() error {
 	if _, err := db.GetEngine(db.DefaultContext).
 		Where(builder.And(
 			builder.Gt{"org_id": 0},
-			builder.NotIn("org_id", builder.Select("id").From("user")),
+			builder.NotIn("org_id", builder.Select("id").From("`user`")),
 		)).
 		Delete(Label{}); err != nil {
 		return err