chore: Remove IsTagExist

- Introduced in 1ebb35b988 and removed in 2af67f6044.

.deadcode-out

@@ -104,7 +104,6 @@ code.gitea.io/gitea/modules/git
 	CommitChangesWithArgs
 	SetUpdateHook
 	openRepositoryWithDefaultContext
-	IsTagExist
 	ToEntryMode
 
 code.gitea.io/gitea/modules/gitgraph

modules/git/repo_tag.go

@@ -5,7 +5,6 @@
 package git
 
 import (
-	"context"
 	"errors"
 	"fmt"
 	"io"
@@ -20,11 +19,6 @@ import (
 // TagPrefix tags prefix path on the repository
 const TagPrefix = "refs/tags/"
 
-// IsTagExist returns true if given tag exists in the repository.
-func IsTagExist(ctx context.Context, repoPath, name string) bool {
-	return IsReferenceExist(ctx, repoPath, TagPrefix+name)
-}
-
 // CreateTag create one tag in the repository
 func (repo *Repository) CreateTag(name, revision string) error {
 	_, _, err := NewCommand(repo.Ctx, "tag").AddDashesAndList(name, revision).RunStdString(&RunOpts{Dir: repo.Path})