[SE-4305] Reordering tabs not working in Koa

[Arti3DPlayer]

Description

In this PR I removed static tabs priority, to make this reordering function works correctly

While we had default priority attribute set for ProgressTab CoursewareTab

get_course_tab_list() 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), we receive this:

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

Supporting information

Jira Issue: SE-4305

Testing instructions

• Go to studio -> Select Demo Course
• On navigation Panel select Content -> Pages (/tabs/course-v1:edX+DemoX+Demo_Course)
• Create new pages and order them with default pages.
  More information here Reordering pages

• Now visit LMS Demo course (/courses/course-v1:edX+DemoX+Demo_Course/course/)
• And check page order

Deadline

ASAP

Other information

[pkulkark]

@Arti3DPlayer LGTM 👍

• I tested this: Verified the pages positions can be moved as described in testing instructions
• I read through the code
• I checked for accessibility N/A
• Includes documentation N/A