Updating wording to specify create/manage project vs group labels in sidebar

• You can currently create a label inline from the issue, merge request and epic sidebars. But sometimes that will be for project labels, and sometimes that will be for group labels.
• This issue doesn't change any functionality. It only updates the wording to be more explicit.
• Regarding the two lines of the text in the screenshot, change them to the following:

Location	Wording
Sidebar in issue page and merge request pages	Create project label and Manage project labels
Sidebar in project issue board	Create project label and Manage project labels
Sidebar in group issue board	Create group label and Manage group labels
Sidebar in epic page	Create group label and Manage group labels