[BUG] Pawtograder does not allow floating point values to be entered into Gradebooks

[dnunez02]

Describe the bug
I cannot enter a floating point value into the Gradebook. This is an issue for imported columns because the workaround is to reimport the column and correct all grade calculations dependent on that reimported column and its slug.

To Reproduce
Steps to reproduce the behavior:

1. Go to a Gradebook.
2. Click on any grade cell.
3. Enter a floating point number like "50.5"
4. See error

Expected behavior
To be able to enter floating point numbers.

Workarounds
Reimport the entire column and change all grading calculations.

Pawtograder Build:
Build: 053a8ff