[DOCS] Updates 7.3 version in data frame analytics API

[lcawl]

Related to #43875

This PR addresses the following CI failures:

10:34:54 org.elasticsearch.smoketest.DocsClientYamlTestSuiteIT > test {yaml=reference/ml/apis/put-dfanalytics/line_85} FAILED
10:34:54 java.lang.AssertionError: Failure at [reference/ml/apis/put-dfanalytics:51]: $body didn't match expected value:
10:34:54 $body:
10:34:54 analysis:
10:34:54 outlier_detection: same [empty map]
10:34:54 create_time: same [1562348094310]
10:34:54 dest:
10:34:54 index: same [logdata_out]
10:34:54 results_field: same [ml]
10:34:54 id: same [loganalytics]
10:34:54 model_memory_limit: same [1gb]
10:34:54 source:
10:34:54 index:
10:34:54 0: same [logdata]
10:34:54 query:
10:34:54 match_all: same [empty map]
10:34:54 version: expected [8.0.0] but was [7.3.0]
10:34:54

[elasticmachine]

Pinging @elastic/ml-core