lock_duration in docu should be corrected

Keyword description of [Fetch Workload](https://robotframework-camunda-demos.gitlab.io/robotframework-camunda-mirror/latest/keywords/camundalibrary/#Fetch%20Workload):

If not provided, this keyword will use a lock_duration of **60000** ms (10 minutes) and set {{deserialize_value=True}}

CamundaLibrary.py line 154, 155: "The default is either environment variable CAMUNDA_TASK_LOCK_DURATION or **600000** (10 minutes)."

line 144 "Value is in milliseconds (1000 = 1 minute)" should also be corrected.

Start by comparing the Fetch Workload documentation with CamundaLibrary.py lines 144, 154, and 155. Correct the lock_duration default and millisecond conversion wording so both descriptions agree, then verify the generated keyword documentation reflects the corrected values.

Written by the indexing model from the issue text.