Fix lineSpacing for slides

[tsaomao]

Current setting at value "10" means make line spacing 10% of normal and squishes all the lines together on the body of the generated slide. value of "100.0" is normal. I think single line spacing. Looks better and is more readable on generated slides.

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[tsaomao]

@googlebot I signed it.

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[tsaomao]

Documentation of the slide text styling API: https://developers.google.com/slides/reference/rest/v1/presentations.pages/text#paragraphstyle