[DOCS] dry_run in docstring of file.blockreplace state, but not implemented

[Timmeeh]

Description
dry_run kwarg is documented in docstring of file.blockreplace state, but not implemented

Suggested Fix
Remove dry_run from the docstring

Type of documentation
Salt Repo

Location or format of documentation
https://github.com/saltstack/salt/blob/v3003/salt/states/file.py#L5614
https://docs.saltproject.io/en/3003/ref/states/all/salt.states.file.html#salt.states.file.blockreplace

Additional context
blockreplace seems to be the only function in the file module that still has this kwarg documented.

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