Goodbye, GraphQL (#24827)

```release-note
NONE
```

server/public/model/custom_status.go

@@ -8,8 +8,6 @@ import (
 	"encoding/json"
 	"fmt"
 	"time"
-
-	"github.com/graph-gophers/graphql-go"
 )
 
 const (
@@ -63,12 +61,6 @@ func (cs *CustomStatus) AreDurationAndExpirationTimeValid() bool {
 	return false
 }
 
-// ExpiresAt_ returns the time in a type that has the marshal/unmarshal methods
-// attached to it.
-func (cs *CustomStatus) ExpiresAt_() graphql.Time {
-	return graphql.Time{Time: cs.ExpiresAt}
-}
-
 func RuneToHexadecimalString(r rune) string {
 	return fmt.Sprintf("%04x", r)
 }