gnucash maint: Use guile-3.0 on Ubuntu-20.04 github-action CI tests.

[John Ralls]

Updated	 via  https://github.com/Gnucash/gnucash/commit/1a8b4820 (commit)
	from  https://github.com/Gnucash/gnucash/commit/854c1178 (commit)



commit 1a8b4820ee03c7ac8d02b58b4bc9f9320d3a4ec2
Author: John Ralls <jralls at ceridwen.us>
Date:   Tue Dec 1 16:26:35 2020 -0800

    Use guile-3.0 on Ubuntu-20.04 github-action CI tests.



Summary of changes:
 .github/workflows/ci-tests.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)