docs: update description for variable strings option
Description
The following user feedback was provided:
Difficult to understand. Create multiple variable in one scheduled pipeline.
This MR improves the help documentation for a command-line tool that creates scheduled tasks. The update clarifies how users can pass multiple variables to a schedule by adding the instruction "Repeat flag for multiple variables" to the existing help text.
This makes it clearer that users can use the --variable flag multiple times when they need to set several variables for their scheduled task, rather than trying to pass them all in a single flag usage.