Fix chart hides map credits

[zoran995]

What this PR does

Fixes #

This is a description of what I've done in this PR, especially explaining choices made to make the reviewer's job easier. If I don't replace this paragraph with an actual description, my PR will probably be ignored.

Test me

• open http://ci.terria.io/main/
• add some catalog item with chart
• observe that map credits line is not visible, and it is actually hidden by chart panel, http://ci.terria.io/main/#share=s-qNjLf5vB5yATlG5Ni82kj9onNFT
• do the same on this branch, map credits line is visible above chart panel

Checklist

• [ ] There are unit tests to verify my changes are correct or unit tests aren't applicable (if so, write quick reason why unit tests don't exist)
• ~[ ] I've updated relevant documentation in doc/.~
• [x] I've updated CHANGES.md with what I changed.
• [x] I've provided instructions in the PR description on how to test this PR.