Change marker type for workbench sample logs plot

[rosswhitfield]

The marker '.' was originally used so that single value logs would be observable, since #23742 there is always two values making this redundant.

Before:

After:

To test:

Compare plotting sample logs before and after this change. For the above plots I used ws=Load('PG3_42941',metaDataOnly=True)

There is no associated issue.

This does not require release notes because workbench

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