Fix planner appearance and layout

[jloh02]

Context/Implementation

Fix comments from @ZhangYiJiang

• Planner settings dialog button using negative margin
• Removal of h1 margin in planner header
• Using sr-only to remove "Settings" label in planner settings button + pure CSS solution

Not sure if the negative margin in planner settings dialog close button is sufficient and looks neat enough. Do let me know how to tweak the margins as required thanks!

Screenshots

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Codecov Report

Attention: Patch coverage is 0% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 53.62%. Comparing base (1e34328) to head (5e22d62).

Files	Patch %	Lines
...iews/planner/PlannerContainer/PlannerContainer.tsx	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #3711 +/- ## ========================================== + Coverage 53.57% 53.62% +0.04% ========================================== Files 273 272 -1 Lines 5984 5979 -5 Branches 1430 1428 -2 ========================================== Hits 3206 3206 + Misses 2778 2773 -5 ```

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