Fix to display site description when logo defined

[Deep-NEC]

Fixes #6111

Proposed fixes:

This fix will allow to use ckan site description even when site logo is defined

Features:

• includes tests covering changes
• includes updated documentation
• includes user-visible changes
• includes API changes
• includes bugfix for possible backport

Please [X] all the boxes above that apply

[Deep-NEC]

Hi @kowh-ai I have investigated ci/circleci: test-python-3 failure, it is failed due to def test_tag_line. In this function it is defined to test the description/tag-line only when no logo and in this PR the fix is to display description/tag-line even when logo is defined. Hence we need to modify the testcase def test_tag_line according to this PR. Please confirm my understanding.

Thanks