Reordering tabs not working

Description

<!--
Please give the pull request a short but descriptive title.
Use [conventional commits](https://www.conventionalcommits.org/) to separate and summarize commits logically.

Use this template as a guide. Omit sections that don't apply. You may link to information rather than copy it.
More details about the template are at https://github.com/edx/open-edx-proposals/pull/180
(link will be updated when that document merges)
-->

  1.  

    1. Description

In this PR I removed static tabs priority, to [make this reordering function](https://github.com/open-craft/edx-platform/blob/esme-oxford-release/koa.2a/lms/djangoapps/courseware/tabs.py#L383) works correctly

While we had default `priority` attribute set for `ProgressTab` `CoursewareTab`

[get_course_tab_list()](https://github.com/open-craft/edx-platform/blob/esme-oxford-release/koa.2a/lms/djangoapps/courseware/tabs.py#L383) returned incorrect order.

Issue is starting from this line where we get all dynamic tabs:

`course_tab_list += _get_dynamic_tabs(course, user)` we are getting correct order.
For example:
`[[10, 'Course'], [inf, 'New Page'], [inf, 'Test'], [inf, 'Discussion'], [inf, 'Wiki'], [40, 'Progress'], [inf, 'Instructor']]`

But after doing sorting next time(for correctly sort static tabs as wee see in [comment here](https://github.com/open-craft/edx-platform/blob/esme-oxford-release/koa.2a/lms/djangoapps/courseware/tabs.py#L383)), we receive this:

`[[10, 'Course'], [40, 'Progress'], [inf, 'New Page'], [inf, 'Test'], [inf, 'Discussion'], [inf, 'Wiki'], [inf, 'Instructor']]`

I removed priority for all Tabs except "Home" and "Course", because in the [official docs](https://edx.readthedocs.io/projects/open-edx-building-and-running-a-course/en/latest/course_assets/pages.html#reorder-the-pages), all other tabs except "Home" and "Course" should be allowed to be re-ordered.

  1.  

    1. Supporting information

Jira Issue: [SE-4305](https://tasks.opencraft.com/browse/SE-4305)

  1.  

    1. Testing instructions

![Screenshot 2021-04-02 at 16 50 19](https://user-images.githubusercontent.com/3278913/113421306-898c7c00-93d3-11eb-8013-6cc479859ec1.png)

  • Now visit LMS Demo course (`/courses/course-v1:edX+DemoX+Demo_Course/course/`)

  • And check page order

![Screenshot 2021-04-02 at 16 51 08](https://user-images.githubusercontent.com/3278913/113421414-be98ce80-93d3-11eb-8984-c151f3e006f3.png)

  1.  

    1. Deadline

ASAP

  1.  

    1. Other information

-

Your pinned fields
Click on the next to a field label to start pinning.

Assignee

Unassigned

Reporter

Open Source Pull Request Bot

Labels

Contributor Name

Artem Hruzd

Repo

edx/edx-platform

Customer

Github Lines Added

0

Github Lines Deleted

3