Currently it is possible to migrate an existing data stream to a time series data stream.
This is done by updating the index template that created the data stream. 
Then after a rollover the data stream is a time series data stream. 

Via a similar way it should be possible to change time series data stream back 
to a regular data stream. Currently when changing the `index.mode` setting
on an index template from `time_series` to `standard` (or removing the setting)
results in a validation error.
modules/data-streams/src/test/java/org/elasticsearch/datastreams/DataStreamIndexSettingsProviderTests.java
String mapping = """
            {
                "_doc": {
                    "dynamic_templates": [
                        {
                            "labels": {
                                "path_match": "prometheus.labels.*",
                                "mapping": {
                                    "type": "keyword",
                                    "time_series_dimension": true
                                }
                            }
                        },
                        {
                            "docker.cpu.core.*.pct": {
                                "path_match": "docker.cpu.core.*.pct",
                                "mapping": {
                                    "coerce": true,
                                    "type": "float"
                                }
                            }
                        }
                    ],
                    "properties": {
                        "host": {
                            "properties": {
                                "id": {
                                    "type": "keyword",
                                    "time_series_dimension": true
                                }