Update ds_covid19au_git.R

[M3IT]

Minor edit to existing ds, fix for the erroneous column names in the data source New source file name with correct column names.

What type of PR is this?

• [x] R
• [ ] other

R

I confirm:

• [ NA] I followed the tutorial
• [ NA] I checked the format with the ds_check_format function
• [ NA] I double checked the data (e.g. coherent with google search)

Additional comments

[eguidotti]

Great thanks!