[OAuth2] org.gitlab4j.api.GitLabApiException: unsupported_grant_type on gitlab 19.3.0

version 6.3.0
gitlab 19.3.0

code `GitLabApi.oauth2Login`

```java
org.gitlab4j.api.GitLabApiException: unsupported_grant_type
	at org.gitlab4j.api.AbstractApi.validate(AbstractApi.java:784)
	at org.gitlab4j.api.AbstractApi.post(AbstractApi.java:423)
	at org.gitlab4j.api.GitLabApi.oauth2Login(GitLabApi.java:348)
	at org.gitlab4j.api.GitLabApi.oauth2Login(GitLabApi.java:151)
```