Fix the toggle sidebar icon on issues/MRs on mobiles

What does this MR do and why?

Closes Unable to collapse issue sidebar when on mobile... (#415240 - closed)

Fix the toggle sidebar icon on issues/MRs/Epics on mobiles when the user is signed out.

Why did this bug occur ?

Earlier with the flag issueAssigneesWidget FF off , the toggle icon was shown with the assignees widget in signed out mode

master with issueAssigneesWidget FF off

When the FF issueAssigneesWidget FF was switched on , the toggle icon stopped being visible on mobiles in signed out mod

What changes here ?

In the signed out mode in issuables , instead of having the icon right aligned with the assignees widget , we will be showing it at the same position as in signed in mode i.e on top of the assignees widget

What do we want to make sure here ?

That the toggle icon in issuables when signed out does not depend on any flag. Hence the behaviour should be the same with the flag issueAssigneesWidget on or off

Screenshots or screen recordings

with issueAssigneesWidget off

Issue Before	Issue After
Screen_Recording_2023-06-27_at_1.37.19_PM	Screen_Recording_2023-06-27_at_1.26.12_PM

MR Before	MR After
Screen_Recording_2023-06-27_at_1.37.45_PM	Screen_Recording_2023-06-27_at_1.27.46_PM

Epic Before	Epic After
Screen_Recording_2023-06-27_at_1.38.09_PM	Screen_Recording_2023-06-27_at_1.29.07_PM

with issueAssigneesWidget on

Issue Before	Issue After
Screen_Recording_2023-06-27_at_1.34.26_PM	Screen_Recording_2023-06-27_at_1.26.12_PM

MR Before	MR After
Screen_Recording_2023-06-27_at_1.35.08_PM	Screen_Recording_2023-06-27_at_1.27.46_PM

Epic Before	Epic After
Screen_Recording_2023-06-27_at_1.35.33_PM	Screen_Recording_2023-06-27_at_1.29.07_PM

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. In rails console enable FF issueAssigneesWidget

   Feature.enable(:issue_assignees_widget)

2. Now visit issue/MR/epics with signed in mode and check all screen sizes , you should be able to toggle the sidebar
3. Repeat the same with signed out , the toggle functionality should be there

Repeat the above steps with issueAssigneesWidget off and verify

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #415240 (closed)