Resolve accessibility issues for better WCAG compliance

[zubairshakoorarbisoft]

Description

Related to overhangio/tutor-indigo#146
On the Teams tab, press left arrow key to bring the focus on “My team” notice that the bottom indicator spreads through all the tabs, and doesn't stay specific to My team's tab, also “Teams” and “Instructor Dashboard” heading(First heading of page) should be H1

Useful information to include:

• All user roles "Learner", "Course Author", "Developer", and "Operator".
• When the focus at the tabs, focus should only move using left right error key, and on enter that tab should become active.
  

After the fix, the focus should move with arrow key without spaning the bottom line on all the tab's bottom, and on pressing Enter key, it should be active.

Supporting information

You can have a look into the following issues to have more context on the issues(Access Required)

• https://tree.taiga.io/project/zaraahmed-tutor-indigo-accessibility/us/49
• https://tree.taiga.io/project/zaraahmed-tutor-indigo-accessibility/us/60

Testing instructions

One can simply pull the changes on local and build image, the changes should be reflected.

Deadline

N/A

Other information

Include anything else that will help reviewers and consumers understand the change.

• Does this change depend on other changes elsewhere? No
• Any special concerns or limitations? For example: deprecations, migrations, security, or accessibility. No Limitations
• No Database Migrations