[Backport 8.x] Fix cluster.get_component_template API

[github-actions]

Backport 1972d83 from #3617.

[github-actions]

Following you can find the validation results for the APIs you have changed.

API	Status	Request	Response
cluster.allocation_explain	🟢	4/4	4/4
cluster.delete_component_template	🟢	2/2	2/2
cluster.delete_voting_config_exclusions	🟢	1/1	1/1
cluster.exists_component_template	⚪	Missing test	Missing test
cluster.get_component_template	🟢	10/10	10/10
cluster.get_settings	🟢	7/7	7/7
cluster.health	🟢	159/159	159/159
cluster.info	🟢	4/4	4/4
cluster.pending_tasks	🟢	3/3	3/3
cluster.post_voting_config_exclusions	🟢	5/5	5/5
cluster.put_component_template	🔴	21/29	29/29
cluster.put_settings	🟢	59/59	58/58
cluster.remote_info	🟢	3/3	3/3
cluster.reroute	🟢	6/6	5/5
cluster.state	🟢	81/81	80/80
cluster.stats	🔴	27/27	0/27

You can validate these APIs yourself by using the make validate target.