Save file dialog's default size is too large for second monitor

## Prerequisites
- [ ] I have searched open and closed issues for duplicates.
I searched for "save file dialog too large", no results for any open issues.

## Describe the bug
A clear and concise description of what the bug is.
I tried to save a file, a save file dialog was opened, but the bottom of window is cut off by the screen, and I can't choose the file name or see the labels on the buttons.

I didn't see a "close" button on the window, not sure if it was cut off as well, but I had difficulty closing the save file dialog window as well.

If applicable, add screenshots or screen recordings to help explain your problem.

[Screenshot from 2020-04-28 15-00-48](https://user-images.githubusercontent.com/18294318/80532606-07453d80-8962-11ea-851b-5fdcdce32b31.png)

### To Reproduce
Steps to reproduce the behavior:
1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

Have a second monitor which has a smaller vertical resolution than the primary monitor, and invoking the save file dialog from an app that is on the second monitor.

### Expected behavior

I expected to be able to see the bottom of the window and choose the name of the file and click the save button.

### Screenshots or screen recordings

### Logs

## Platform Information

- [ ] I'm using the latest version from git that I've manually compiled
- [x] I'm using the latest released stable version

`uname -a:
Linux my-computer 5.3.0-46-generic elementary/files#38~18.04.1-Ubuntu SMP Tue Mar 31 04:17:56 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux`

## Additional context