Parsing of float in workflow

[jwarner8]

Parsing a float into the workflow to generate the task name causes errors, as a period is not an acceptable character in the cylc workflow. This change parses the dot into a p for the workflow task names.

There might be a more general solution we could apply though, as I expect this might crop up with other diagnostics/variable combinations in new recipes.

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[github-actions]

[jfrost-mo]

Looks good to me. A more general fix will come as part of the data time cycling, but this looks good for the current issue.