Remove sliding glass doors from a fiberglass bathtub/shower?

I own a home that was constructed in 1979. The bathrooms have fiberglass showers with sliding glass doors. I have removed the sliding glass doors and replaced with shower curtains to update the appearance; however, I have not removed the tracks. It looks like I can unscrew the tracks from the tub (6 screws total) and scrape and clean the caulking; however, I was wondering what I could use to fill the screw holes. Any help would be appreciated. Please advise.

Thanks,

Troy